The Lamb

The one who's quiet, shy, and has a "soft" personality, meaning they don't hurt anyone, say vulgar words, do immoral things, and they have some sort of harmless goal, like marrying The Hero. This person is supposed to be cute because of all of these things.

The Lamb got their name from, of course, a lamb, an animal that you wouldn't expect to hurt anyone, acts a bit shy, and is found to be cute by many.