Undertale

Undertale is an indie video game that was published in the year 2015. Many fans claim that it has original characters, dialogue, humor, and gameplay. Undertale was produced by Toby Fox and is available on Steam for purchase.

The premise of Undertale is that it is an RPG that plays on the expectations of any other game of the genre: in a typical RPG, the player is meant to kill enemies they encounter to become stronger, while in Undertale, if the player does so, they will be shamed and, if they continue this behavior, feared and hated by the characters. The game acts as a test of the player's morality through how to choose to treat the NPCs in battle. Very early in the game, the player is told that it is possible to win battles without hurting or killing their opponents. If they refuse to hurt the monsters they encounter, the player will be rewarded with what is considered the true ending to the game.

Pre-Credits Story
(The briefing of Undertale's story will assume that the player has decided to go down the True Pacifist path in the game.)

Before the real game begins, the player is given a summary of the war between the humans and the monstersundefined, as well as an explanation of how their character (the one named Frisk) wound up in the underground. After this backstory, the game begins. Moving in the only direction available to them, Frisk quickly encounters Flowey, a sentient, talking flower who acts as a guide to the world of the monsters. He introduces Frisk to their SOUL, the game's battle system, and objects that he calls "friendliness pellets". If the player knows what's up with Flowey, he will grow impatient with them not hitting his pellets, which he will become aware of and attempt to punish the player for with death. Fortunately for Frisk, a kind, motherly goat by the name of Toriel Ex Machinas to save their SOUL from an inescapable ring of bullets by One-Shotting Flowey with a magical fireball attack. She proceeds to guide Frisk after they pass a series of puzzles and learn how to ACT when encountering monsters. At the end of the road of puzzles, Toriel takes Frisk to their new home: hers. This gives Frisk the opportunity to explore their new living space and chat with Toriel if they're in the mood to converse with her. Homesick, Frisk asks Toriel about how they can possibly return home, which prompts the goat mother into heading downstairs where she plans on destroying the way to the rest of the underground. Frisk follows her down to the tunnel leading out where she tells them that it's best they stay with her as they would only die if they ventured out to the rest of the underground, being killed by Asgore for their human SOUL if he ever happens upon them. Frisk refuses to listen to Toriel, which initiates a battle to prove if Frisk is capable of surviving in the world of the monsters. After Frisk wins by repeatedly SPARING Toriel, she bids Frisk farewell and tells them to not try to return to her home before they step through the gates leading out of the RUINS.

Shortly after escaping the care of Toriel, Frisk encounters Flowey a second time where he judges them based on their actions in their duel with Toriel (including their past saves and gameplays if such exist and can be remembered by the game). If the player has continued down the True Pacifist route thus far, Flowey will downplay the fact that they spared one person's life and share that he plans to reach the surface and spread his philosophy throughout the world. After Flowey sinks back into the ground, Frisk continues to the next doorway where the game's logo and name appear on one screen, a second screen reads "By Toby Fox", and a final screen cuts to black.

As the real game begins, Frisk heads down a snowy path, beginning their new adventure. By the time they reach a short bridge, a Mystery Silhouette that has been following them since they left the RUNS creeps up to them, requesting they turn around and shake its hand. When Frisk does, a long whoopie cushion noise is made as the shadow is illuminated, revealing a skeleton in a blue jacket and black pants. It's Sans. He introduces himself and tells Frisk about Papyrus, his human-hunting brother that Sans initially helps Frisk hide from by telling them to take cover behind a conveniently-Frisk-shaped lamp. When Papyrus makes the scene, he chastizes Sans for being lazy and not doing his job with his puzzles or looking out for the human. Sans coolly plays off his slothfulness and waits for Papyrus to leave so he can tell Frisk to come out of hiding, which they do. Before Frisk leaves, Sans calls out to them and asks if they can cheer Papyrus up by continuing to be a human, which they agree to do by playing along with his puzzles. Papyrus, right up ahead on the snow-covered path, talks to Sans until he spots Frisk and tells them his plan to capture them, become popular, and be put on the royal guard. Frisk continues down the icy path until they meet Sans and Papyrus again, also facing their first puzzle from the brothers. Papyrus explains it as an invisible electric force field that Frisk must navigate with an orb on their head. Once the puzzle has been defeated, Sans and Papyrus move on the puzzle Sans set up, which is a word jumble the player cannot actually do. Frisk quietly passes the jumble and resumes their travel after the two others proceed down the path. Outside of puzzles, the next time they see the skeleton brothers is when Papyrus is on the verge of overkilling Frisk with a deadly six-part Death Machine known as the Gauntlet of Deadly Terror as they stand on a bridge. He hesitates to activate the machine (which he lies about not doing), then chooses to turn back on his actions and call off the contraption. Before leaving, Papyrus does his trademarked "nyeh heh heh!" with the final "heh" being followed by three question marks, implying his being pondered by his own decision about saving the human's life.

Soon after Frisk crosses the rest of the bridge, they find themselves in Snowdin Town. They make an attempt to go to the far east, but are blocked off by Papyrus who begins to battle them in an attempt to capture the human who could help achieve his dreams. When Frisk finishes their battle with Papyrus, he feels ashamed that he couldn't even defeat a small human child, saying that he will never be able to join the Royal Guard. As Frisk offers to be his friend, his spirits immediately raise and he invites his new friend to a date at his houseundefined. It's optional to follow through with the date, but if Frisk pushes forward to befriend Papyrus, a necessary step in achieving the True Pacifist ending, they will be let into the skeleton brothers' home where Papyrus gives them a tour of the place. When Frisk is interested in going into Papyrus's room, he will offer a second tour to the room. There, Frisk and Papyrus can begin their date where Papyrus will make multiple attempts at deescalating the date only for Frisk to successfully max out their Date Power with him. In the end, Papyrus figures that he can't return the feelings the human has for him and that the two can only be in a platonic relationship, then lends Frisk his phone number.

To advance in their adventure, Frisk will need to go east to the marsh. As they step into some tall grass, Papyrus approaches a character clad in armor, Undyne, and tells her that he failed to capture the human who fell into the underground. Disappointed with Papyrus's failure, Undyne tells him she plans to take the human's SOUL herself. Papyrus reluctantly agrees to help her in any way he can, then heads for his home in Snowdin Town. Frisk resumes their traveling through the marsh and encounters Undyne multiple times. As they avoid Undyne's relentless attacks on them, a monster known as Monster Kid — presumably Undyne's biggest fan — follows them through their hike, praising Undyne's name all the way. At one point, Monster Kid makes a failed attempt at hating Frisk (per Undyne's indirect order) as the two meet up on a bridge, then tries to run off and go home. As he normally does when rushing away, Monster Kid loses his balance and trips off of the bridge, clutching onto the rocky side of the bridge. Undyne walks up to Frisk, then potentially makes a gesture at the player to tell them what they should do to help the fallen Monster Kid (lifting her arm as if she's pulling the kid up). After helping Monster Kid up back onto the bridge, he defends Frisk and says that if Undyne wants to fight them, she'll have to deal with him first. This causes Undyne to back off and head the other way. The decision Frisk made to help Monster Kid successfully befriends him. Not too long later, Frisk meets up with Undyne for the final time as an enemy where they begin their real battle with her. As they fight her, Frisk must FLEE whenever the opportunity arises in battle and run away from Undyne, eventually making their way to the HOTLAND where Undyne will struggle with continuing with her hot armor. Conveniently, a water cooler happens to be right where she would need it, but her only hope of hydration is if Frisk pours a cup of water on her, which they decide is the right thing to do. With the strength to stand up, Undyne leaves Frisk alone, allowing them to continue down the stone path in the HOTLAND.

An optional part to the story that is required for the player to get what is called the true ending to Undertale is guiding Frisk back to Undyne's house in the marsh where they will meet Papyrus standing outside of the fish-shaped home. He helps Frisk meet with Undyne as friends for the first time, which she is shocked and offended by, suspecting Frisk of wanting to humiliate her after she failed to take their soul. In a scary twist, Undyne changes her mind and decides that being impossibly good friends with Frisk would be the best Revenge Plot in that situation, resulting in her using intimidation to make Frisk a good house guest. Undyne offers Frisk a drink before giving them a spear with which they can make their selection. The only choice that will progress is selecting the tea, which Undyne prepares for Frisk. With Frisk now comfortable? in her home, Undyne tells her backstory as a hardheaded kid who was challenged by King Asgore in a spar. Time and time again, she'd lose to him, but once, she beat him, which made her feel guilty of harming such an innocent individual who only dodged her attacks as opposed to striking back. After years of training from Asgore, she was made the captain of the Royal Guard. At the end of her tale, Undyne realizes that Papyrus left before his cooking lesson, which she passes on to Frisk in hopes of the two becoming friends. This over-the-top cooking (either on the behalf of Frisk or Undyne depending on how the player chooses to prepare the noodles) is what causes Undyne's house to wind up in flames. At first, Undyne considers herself a failure for not being able to successfully fight or befriend Frisk, which leads to her pinning the blame on Frisk. She battles them, offering the first hit to her opponent, who then lands the third worst hit in the history of everything. Undyne is dumbfounded by the 1-damage attack, but then turns her attitude around after Frisk's pathetic attack reminded her of someone she used to train. With her house now just dead, Undyne heads out to move in with Sans and Papyrus after giving Frisk her phone number. With Undyne now allied with them, Frisk can now backtrack to the HOTLAND and resume the main story.

After progressing in their journey, it doesn't take long for Frisk to encounter a lab, which they enter without invitation. There, they meet Dr. Alphys, a dinosaurundefined-like scientist who introduces herself before telling Frisk of one of her inventions named Mettaton, an entertainer-gone-human-murderer robot whose body has been outfitted with anti-human combat features, meaning Frisk cannot fight Mettaton with forceundefined. Soon after, Mettaton shows up by blasting through the wall of the lab and challenges Frisk in a quiz show-style battle where they cannot hurt him and the only way he can hurt them is if they get an answer wrong. When Frisk completes the series of questions, Mettaton leaves them be for the time being. Frisk exits Alphys's lab and sets down HOTLAND's next path where they will later encounter Mettaton and his unending madness multiple times over. The last time they suffer under Mettaton and his infernal bull is when he reintroduces the colored tile puzzle that Sans and Papyrus used earlier in the game. When defeated, he anticlimatically wheels away in battle, letting Frisk go further down the path ahead of them.

Nearing the end of their adventure, Frisk reaches the CORE, the towering building that leads to Asgore's castle. Alphys, somewhat desperate to do the right thing for Frisk, makes numerous failed attempts at guiding them correctly through the CORE. But even without her help, Frisk manages to navigate through the maze-like building and eventually encounter Mettaton yet again. Instead of forcing them through some entertainment-like stunt, he tells him about Alphys's secret plan to insert herself into their adventure so she can feel like she's a part of the story and be considered a heroine by Frisk. After this Big Reveal, Mettaton continues to share with Frisk that he did not have any intentions of hurting them and only wanted to entertain humanity when he passed the barrier. Despite this, Mettaton continues to battle Frisk and entertain an unseeable audience of monsters in his new form known outside of the game as Mettaton DX. When this spat ends, Alphys rushes into the room, checks on the defeated new Mettaton, and follows Frisk into the next hallway where she admits that she lied about the barrier. Instead of only a human soul being needed to cross it, both a human and monster soul are required to pass the wall, which means Frisk must kill Asgore to return home.

Entering a location called New Home, Frisk is told a story through a series of monsters. The first human to fall into the underground was discovered and helped by Asriel, the prince of the kingdom of monsters. As time went on, the two became like siblings, and the king and queen viewed the human as their own child. One day, the human became lethally sick and died shortly after, much to the despair of Asriel. He absorbed the human's soul, crossed the barrier, and placed their body on a bed of golden flowers in a human village, as it was their Final Wish. When the villagers spotted Asriel with the dead child, they thought he killed them and brutally attacked him. In spite of having enough power to annihilate every one of the humans, Asriel only endured their tormenting and headed home after the beating, seriously wounded from his punishment. Eventually, Asriel could not carry on after being in such a critical condition and died, his dust spreading over the king's garden. Infuriated by losing two of his children in a single day, King Asgore declared war on the humans with the plan of using the soul of every human who fell into the underground to break out of the prison the monsters were forced into. As the humans gradually fell into the underground, six of their SOULs were collected out of the seven necessary to shatter the magical barrier, meaning Frisk is the final SOUL the monsters need to break free and roam the surface world again.

Frisk steps into a corridor that leads to Asgore's throne room. There, a dialogue box tells them the definition of LOVEundefined and EXP, which are acronyms for "level of violence" and "execution points" respectively. When a monster dies to the player, they collect execution points which indicate how much an individual has harmed others, while their level of violence shows how much they can hurt others. At this point, Sans is meant to judge the player and tells them what their actions through the course of their gameplay meant, but if they are continuing down the True Pacifist route, Sans will instead praise how they haven't collected either LV or EXP. After he suddenly disappears, Frisk is allowed to progress and begin facing the king.

Heading into the throne room, Frisk quietly approaches Asgore who is faced away from them. He turns around and, upon finding the human, is surprised and disheartened to find them before him. Before and as he heads into a hallway leading to the barrier, Asgore expresses how he would prefer to treat Frisk as company instead of an enemy but understands that he must push on and battle the human. During their battleundefined, Frisk must do something that they haven't before during their travel: fight a monster using violence.

When Asgore's health is dropped to 0 by Frisk, he shares why he declared war on humanity and adds that his wife, the queen, left after he did so. All he wanted was to see everyone live their lives with hope, not the power he has as a king. As Frisk is given the option to use MERCY on Asgore, he is amazed at the human's forgiveness and promises them a life of love with him and the queen. At the end of his monologue, a ring of familiar white bullets surrounds King Asgore before homing in on him, destroying his body, and shattering his SOUL. Flowey appears out of the spot Asgore was kneeling in and, with the six human SOULs surrounding him, reminds the player once again that "In this world, it's KILL or BE killed" before force-crashing the game.

When the player boots the game up againundefined, they will be greeted with what appears to be the standard starting screen, but it has now been altered by a maddened Flowey who creates his own version of saving and loading the game, a system he plans on using to eternally punish Frisk with an infinite number of deaths. Absorbing all of the other six SOULs, Flowey becomes a godlike abomination known as Photoshop or Omega Flowey. Frisk, alone in the void, must fight this beast in the game's truest bullet hell.

After Frisk has been assisted by each of the other human SOULs during their battle with one of the game's final bosses, Photoshop Flowey decides to end them for good, but his file save/load system fails and gives the SOULs a chance to revolt against him, reducing him to a beaten-up version of himself. At this point, Frisk can either FIGHT Flowey and destroy him once and for all or continue down their path and MERCY him. He refuses to be MERCIED and begins to tell Frisk that it won't do any good to continuously spare him, then he threatens to kill Frisk, everyone they love, and everyone else. Continuing to MERCY the flower will cause him to admit he doesn't understand why the human is treating him with such kindness after everything they've been put through by him, then disappears. Frisk is left to exit the room and go through the gateway they met Toriel near, which they do.

Cue Credits.

After the credits roll, Frisk is called by Sans some time after their fight with Asgore and tells them how things have been since they were last seen. At the end of this call, Flowey pops up again and asks the player why they let him escape what could have been their wrath. He then lets them in on some information about a better ending to their story, which Bends The Fourth Wall, and advises they see at least one of their friends depending on the call Frisk gotundefined. Flowey then leaves again with a smile on his face.

End Game Story
Frisk returns to their probable last SAVE point — the save known as Throne Room — and should backtrack to the MTT Resort where Undyne will call them, saying she has something for them to deliver from Snowdin. Frisk takes the cue to head back to Snowdin to meet up with Undyne where she will hand them a letter to give to Alphys. Frisk has fun while they return to the place they jjjjjust came from and walk up to the scientist's lab. Alphys opens the front door to see Frisk was the one who delivered the letter which turns out to have said something she considers "adorable" and "surprising". She then says that she'll do as the letter requested, which was to go out on a date. The two try to date right on the spot, but Alphys continuously causes delay before moving the date to the most romantic spot in all of the underground: the garbage dump. Alphys and Frisk are about to begin their "date" until Undyne shows up, causing Alphys to go into hiding behind a garbage can. After Undyne leaves, Alphys comes from behind the can and reveals to Frisk that she likes Undyne. Soon, the two decide the best course of action to take next is to roleplay Alphys dating Undyne, then decide who must be Undyne. Near the end of this simulation, Alphys accidentally lets the truth out in front of Undyne as she yells "I'M UNDYNE AND I'M PULLING ON THE SMOOCHES!". Out of lies to tell, Alphys then tells more of the truth to her love who comforts her before throwing her into a trash can. Undyne tells Alphys that she doesn't care if she was lying all along and likes her for who she is, then offers to train her, only to reveal that Papyrus will be her real coach. Papyrus and Alphys then run off do 100 training laps around the dump, leaving Frisk alone with Undyne. She then asks if anime is real or not, then, regardless of Frisk's reply, leaves the dump.

When Frisk makes their way to the exit of the dump, Papyrus calls them, saying that he strongly feels for no reason that they should go to Alphys's lab and check in on her before hanging up. When Frisk does as Papyrus advises, they will be allowed to enter the True Lab, where it is then impossible to abort the True Pacifist Route. Shortly after entering the True Lab, Frisk will be confronted with a door that requires four differently-colored keys. As they go for these keys, Frisk encounters grotesque monsters known as amalgamates, fusions of monsters who were filled with too much determination and whose physical forms melted into each other. The objective Alphys, their creator, was aiming for was to create the power of a SOUL that cannot be artificially recreated, therefore leaving the only option of harnessing it from the bodies of monsters who "fell down". With enough SOUL power caused by determination, Alphys could make the final SOUL needed to shatter the barrier. A body would need to hold this power, but since a member of one species cannot absorb its own species' soul, Alphys required something that was neither human nor monster to carry the SOUL power after it gained the will to live, resulting in Flowey.

When Frisk collects the four keys, they're allowed to go through the key door and activate the power for the elevator. After they flip it on, a line of amalgamates slowly approaches them until Alphys steps in to stop the monsters. She then proceeds to summarize her purpose in the True Lab that the walls' entries explain in more detail. Alphys makes the decision to tell the fallen monsters' families about what happened to their loved ones before heading out of the room.

Frisk is allowed to return to the activated elevator where they receive a call from a voice they have never heard before. The voice tells them that whatever plan it might have is going to succeed thanks to Frisk's efforts and that it is going to see them soon. Taking the elevator returns Frisk to the king's castle where it seems that they've traveled back in time to before they fought Asgore. He behaves as if the two are about to fight until a familiar fireball is summoned to knock him off-screen. Toriel steps into the battle room and confronts Frisk, giving them a similar greeting to when she first met them in the RUINS. She tells Frisk that she had to check in on them since she couldn't stop herself from worrying and that they would have had to make a terrible choice if they continued. Asgore is glad to see his ex-wife again, but Toriel is still ashamed of him and his actions, stating that he could have taken the SOUL of the first human, passed through the barrier, and returned with six other humans' SOULs to free the monsters peacefully as opposed to sitting in the underground and waging war on humanity. Suddenly, Undyne walks into the room out of nowhere, followed by Alphys, Papyrus, and finally. Sans. When asked about how he rounded everyone up, Papyrus says a flower helped him, which summons Flowey into the room after one of his vine tentacles wraps everyone up. He reveals that he took the human SOULs while everyone was being buddy-buddy with each other and that the best part of it all is that Frisk is the one to blame for the mess everyone is in. He explains to either Frisk or the player that he went back to his old ways because if Frisk leaves the underground, they win the game, and if they do that, Flowey won't have anyone anymore. Right as Flowey is on the verge of killing Frisk, Toriel intervenes with a protective ring of fireballs around their SOUL, saying that no matter what happens, she and the others will always back Frisk up. Flowey makes repeated attempts at killing the human only for their friends to block his shots. Eventually, all of the monsters in the underground face Flowey, completely outnumbering him. Flowey pretends to be in peril, then absorbs the SOULs of all the monsters and awakens his true form: a goat child by the name of Asriel Dreemurr.

Frisk is left truly alone in the void to battle Asriel who says he only wants to reset everything with his new power so Frisk will lose to him time and time again, and so everyone will go through the same cycle eternally. As Frisk continues to refuse to give up, Asriel enters his final form, which causes Frisk to be unable to do anything but struggle against his power. Possibly beginning to lose hope, Frisk realizes that if they can't SAVE their game, they can SAVE something else.

In the penultimate act of Undertale, Frisk begins to save the SOULs of their friends through the small amount of power they still have. They do this by doing or saying things that remind the Lost Souls — empty versions of Frisk's friends who have lost all of their memories — of who they were before Asriel struck. After everyone has been saved by Frisk, they now only have one option for their SAVE selection: Someone else. When Frisk wonders who it is they need to save next, they realize that the last person they have to save is deep in Asriel's soul, then calls their name out. This triggers a cutscene about when Asriel found the first human after their fall, then transitions back to the battle. Frisk calling the last person's name fills Asriel with a feeling he can't understand, so he continues to fight Frisk. Not giving up on saving the last soul — Asriel Dreemurr — Frisk persists in their attempt to save him, which soon causes Asriel to admit that Frisk is the one he cares about most and who's still any fun to play with. In a final attempt to win the battle, Asriel blasts Frisk's SOUL with a rainbow laser that destroys all of the menu selection boxes but SAVE and causes Frisk's health to drop to a tiny decimal. Still holding on to the sliver of health they have, Frisk stays alive while Asriel tells them that he's alone and afraid before he reverts to his original form, sobbing into his arm.

Now with the last battle of the game over, Asriel realizes that the one before him isn't really the first fallen human (Chara), but instead a look-alike named Frisk, the eighth fallen human. Frisk lends their real name to Asriel, who compliments the name and thinks it's nice. Asriel tells Frisk that when he was in his Flowey form, he lacked a soul and therefore couldn't love or feel compassion towards others. Now with the soul of every monster inside his being, Asriel feels that they all care about each other as friends, family, and other loved ones. Believing that Frisk might hate him for his actions, Asriel expresses how he understands their possible sentiments and how what he did was unacceptable. Frisk, being the ever-benevolent person they are, forgives Asriel in spite of all his past misdeeds, which cheers him up and prepares him to free everyone's souls. He levitates into the air, releases the six human and thousands of monster SOULs into the world, and finally destroys the barrier the humans from long ago cast on the monsters, releasing the prisoners back into the surface world. Without the power of the many souls in his body, Asriel faces the inevitable fate of reverting to Flowey where he cannot feel love for anyone again. Before this, Frisk comforts him, hugging him closely. Asriel then walks away, giving his parting wish to Frisk that they take care of Toriel and Asgore while he's away.

Frisk wakes up in the room before The End where his friends surround them. Seeing that nothing bad has happened to Frisk, they all feel relief. Toriel introduces the options of either going around the underground and talking to everyone or simply heading through the last gate where their journey will really endundefined. If the player wishes to go through the gate at any time, a final scene of Frisk and their friends plays. Everybody marvels at the beauty of outside, admiring the Sun and its light. Toriel mentions that, although it is nice to finally be free, the group must decide what comes next in their new lives. Asgore offers Frisk the chance of being the ambassador of the monsters as they meet with the humans, which is a choice the player can make. If they accept, Papyrus will gladly leave the group with intentions of being "the best mascot" for Frisk. Sans is next to leave, making sure that his brother doesn't get himself into too much trouble, notably heading off in the wrong direction as he often does. Undyne follows after Papyrus, going in the correct direction, then Alphys rushes after her, leaving Frisk, Toriel, and Asgore. The king then hurries after everyone but Sans, wondering if he should do something about them. Since Frisk is native to the surface world, Toriel figures that they must have a home to go back to, which is a second choice that the player can make: the first option causes Frisk to live with Toriel, and the second shows a picture of them with their friends. After their selection has been made, the True Pacifist Route credits roll before a final scene plays depending on the player's last choice in the game.

Cue Credits.

Post Credits Scene
If the player opens their game after the credits, Flowey appears one final time. He talks directly to the player, saying that everyone is living their lives in peace and happiness since there are no longer any threats to them and assuring the player that there is nothing to worry about. The only real threat to the monsters at this point is the player themselves who wields the power to reset the game and set everybody back to the underground. Flowey feels and understands the player, reminding them that he once had that power before the eighth fallen human descended into the underground, but also shares that he would never use that timeline-altering power if he had it after the true happiest ending to the game. Flowey pleads the player to not reset their game and just let everyone live with what they have now that everything is perfect for them in their new lives. A moment of silence happens before Flowey says if he can't change the player's mind, they'll have to put up with him and his soulless attacks on them again. He then continues to acknowledge the possibility of the player having heard from him "hundreds of times" before disappearing with his parting words: "See you later... ."

Genocide Route
Of course, the player doesn't have to be a weiner and refuse to fight anyone through their play of Undertale. They could also do the complete opposite of this and kill every fightable monster they encounter.

If the player wants to go down the Genocide Route and play what is known by fans as a Genocide Run, they can, as stated less than a sentence ago, kill every enemy in the game. In case this is true, every major area in the game — RUINS, SNOWDIN, MARSH, HOTLAND, and COREundefined — has what is called a monster counter. Starting from when the player has killed every monster in the RUINS, they will see a counter at their SAVE points saying "[X] left.", referring to how many monsters there are left to kill in the current area. After the counter has been brought down to 0 and that location has been exhausted of its enemies, the SAVE point will instead read "Determination.", random encounters will be replaced with empty battle rooms, and the area's music will ominously slowundefined. This will also change events and character's dialogue from exiting the RUINS forward, which we will be getting into now.

Genocide Route's Story
As implied before, the Genocide Route's story does not begin until the player has left the RUINS after they have killed all 20 monsters in the RUINS, excluding Toriel who is also a required kill to achieve the Genocide Route ending. Like on any other run of the game, Frisk will head down the snowy path leading into Snowdin with Sans eerily tailing them. After he plays his Whoopie Cushion prank on Frisk, he tells them that now is the time to laugh, then notices how their face is devoid of any form of emotion. Leading Frisk through the gate, Sans tells them to hide behind the conveniently-shaped lamp, but Frisk doesn't move. Papyrus shortly runs over to Sans and asks if he's found a human yet, to which he replies "yeah.". Instead of getting on Sans's case for being lazy, Papyrus simply turns the other way and leaves. Before Frisk leaves, Sans calls to them and says it'd help him if they cheered Papyrus up by continuing to pretend being human, aware of their unhuman behavior and possibly their genocidal acts in the RUINS. Continuing to the right will trigger an alternative scene to Papyrus announcing that he plans to capture Frisk the human: in the Genocide version, the skeleton brothers will seemingly struggle to identify Frisk as a human being, which is contrasted to their immediate recognition of them as human. After Papyrus realizes that Frisk is a human, he warns them of the wacky times ahead he and Sans have in store for them, then bolts off. Sans then comments on how Frisk didn't even blink once during the scene before following his little brother. The next time Frisk meets the skeleton brothers is during their first puzzle. Instead of playing along and doing the puzzle, Frisk simply walks through as Papyrus tries to explain the electrical maze to them. Papyrus is disappointed to see Frisk ignore the puzzle and sad leaves the area. Every puzzle until the colored tile puzzle has already been solved for Frisk, which makes going through Snowdin faster. When Frisk makes it to the next puzzle, they ignore it like how they did the electrical maze. This further lets Papyrus down and causes him to leave behind an unreadable paper before heading to the Gauntlet of Deadly Terror. There, Papyrus catches on to Frisk's puzzle-skipping habit by saying they'd likely just walk through it like how they have everything else. After the discussion between the brothers, Papyrus leaves for Snowdin Town. It's at this point the player can talk to Sans and hear one of his now-famous lines: "if you keep going the way you are now ... you're gonna have a bad time."

Entering Snowdin Town, the player will get a view of the most major Genocide Route change thus far: Snowdin Town has seemingly been abandonded. Going into the town's shop opens Frisk up to stealing from the place, the inn is void of any residents, and the only one still in the area is Monster Kid. Traveling to the far west and encountering Papyrus will initiate a Genocide-exclusive scene: Papyrus will stop the human in their tracks as he normally does, then shares how he feels about them. He tells them they're strange since they avoid puzzles, always have dust on their hands, and walk in an awkward pattern. Papyrus notices that Frisk is making a series of poor decisions in their life and offers to help steer them in the right direction as he sees they still have time to become a good person. All this time, Frisk steadily approaches the skeleton before them. This begins the Papyrus "battle" as he foolishly overlooks the fact that Frisk is not okay. In this battle, Papyrus immediately offers to SPARE Frisk as a starting lesson about not hurting people. To not abort the Genocide Route, the player must One-Shot Papyrus who departs with his Final Words, saying he still believes in Frisk.

Frisk continues venturing to the marsh where they will meet Undyne. As Papyrus is no more, she will instead more quickly notice Frisk as they walk through the tall grass, ready her spear, and search for whoever made the noise. Seeing nothing, she disappears and begins her hunt for Friskundefined. This running from Undyne ends on the bridge where Monster Kid will confront Frisk, saying that Undyne told him that Frisk is a bad person. He doubts this and continues to have faith in Frisk, but they only return the favor with an attempted attack. Instead of hitting Monster Kid, Undyne steps in and gets hit in his place, getting One-Shot in the process. She tells him to go home to his parents, which he promptly does, then battles Frisk in her strongest form, Undyne the Undying.

At the end of this fight, Undyne dies for real with her body melting before she turns to dust. Frisk is allowed to proceed to the HOTLAND and make their way to Alphys's lab. Reaching the lab reveals only Mettaton since Alphys, as he explains, is busy evacuating the monsters to a location Frisk can't get to. He quickly runs off to the CORE, which is also Frisk's next destination. Without Alphys around, going through the core is as simple as taking the elevator to the room Mettaton waits for the human in. He says that Frisk is a threat to both monsters and humans, which would leave him with no audience on the surface. He then transforms into Mettaton NEO, his worst and weakest form that only stands in place and can't even be SPARED.

Swiftly moving on, Frisk takes the elevator to New Home where they're encountered by Flowey again. Popping out of the ground in his usual way, he begins telling Frisk his backstory in a style similar to the non-Genocide backstory behind Asriel and the first fallen human. He begins his story by asking if Frisk remembers when the two of them spent time playing with each other in New Home, continuing to mistake Frisk for the first human. Flowey then recalls when he first woke up in New Home's garden and began panicking as he realizes he was transformed into a flower. When the king found Flowey, he told him about his horrifying experience of becoming a flower. Even though the king was filled with emotions, Flowey felt nothing on the inside. After weeks of making failed attempts at feeling any form of emotion again, Flowey ran away from home and returned to the RUINS where he met Alphys. He wished for someone he could love, but without a soul, Flowey lost sight of the meaning of his life and "followed in [Frisk's] footsteps" by "removing [himself] from existence". After he died, Flowey woke up and found himself back at his last SAVE point as if his dying were only a nightmare. He used his new power to toy around with other people and figure out what would happen if certain events happened. As time went on, Flowey lost enjoyment in becoming friends with people whose lives he improved as he essentially 100%'d the world of the underground. With everyone and everything in life becoming bland, Flowey turned to a life of murder, then comments on how Frisk must know how exciting it is to kill anyone in sight before Bending The Fourth Wall by saying people who kill are above those who only wish to do such but are too pathetic to satisfy their desires and only watch murder, such as the player. Flowey then continues to compliment Frisk for their impulsive and unpredictable behavior before he tells them he's ready to break the barrier and spread his prophecy throughout the world. But first, they would need the king's six human souls, including Frisk's, to shatter the barrier. Flowey says he's still planning to do this because Frisk is the only one who understands him, saying that those with their mentality wouldn't mind getting rid of others who get in their way. Suddenly, the music stops before a new song begins playing. Flowey's body begins to shake uncontrollably as he begs for forgiveness. Frisk refuses to listen to him and proceeds down the path, quickly wearing down on his composure.

Frisk silently continues into the Final Corridor where they encounter Sans. He initially asks them a question — if they believe anyone can be a good person if they try — before if they want to have a bad time. This begins the most well-known fight in the game with the most heavily-memed song in its soundtrack.

If Frisk manages to defeat Sans in the battle he anticlimatically slides out of, they can continue to the king's throne room. Upon arrival, the king says to himself how he's never seen a flower cry before turning and seeing Frisk standing behind him. As Asgore is talking to Frisk, they initiate battle, cutting him off mid-sentence. He makes an effort to deescalate the situation only to be killed by Frisk without the player's input. Flowey's pellet bullets appear in a ring around Asgore's body and finish the job, his way of showing how he can be useful to Frisk. Flowey begs with tears forming in his eyes for Frisk to not kill him, eventually revealing his identity to be Asriel by morphing his face into that of his former self's. Frisk ignores the flower's pleads and finishes him off with multiple slashing attacks, reducing him to nothing.

After five seconds of blackness, a human child shows up on the screen. They introduce themselves as Chara and thank either Frisk or the player for awakening them from their death. Chara says that were wondering how they were resurrected after their plan with Asriel failed, then realize that the cause of their return was the one who guided them through Frisk's journey. And now that everyone has been destroyed and Chara has become as strong as they can become, they decide it's time to destroy the world before they repeat the cycle in another world. If the player chooses to erase, they will entirely undo their gameplay and reduce the world to ruins. If they refuse, Chara will feign confusion, then ask the player when they were in control before jumpscaring them and continuing to destroy the world regardless of the player's input.

Post-Genocide Scene
If the player reboots their game, they will be met with nothingness and the sound of a howling wind. If they keep the game open for ten minutes, Chara will return (although only text will appear on the screen), finding it curious how the player now decided they want to return to the world they crushed. Chara then makes a deal with the player, saying they will accept their SOUL in trade of recreating the world. The player must take this offer if they wish to play the game again or else they will sit in the void until the end of time. The game will then force-crash and be ready to be played again once the player has made their One-Way Choice.

Second Post-Genocide Scene
If the player has destroyed the world a second time on a subsequent Genocide Run, they will be confronted with Chara who has an alternative dialogue prepared. They will give the player a greeting similar to their first meeting, then say that the SOUL they acquired from the player the first time is "wracked with a perverted sentimentality", which would explain why they continuously create and destroy the world. After this baffling behavior on the player's behalf, Chara loses understanding of the player's motives, yet still feels it'd be best to create the world again with hopes of a better outcome from the player's possible next gameplay.