I'll ask here because this is an anime-related question more than linguistics. Dozens of anime series over the decades come back to this as a key motivation -- the hero finds "someone to protect" which leads to a turning point and/or a new source of strength. Dubs of all kinds translate it that way exactly. It's not always a question of belonging, family, noblesse oblige, or duty to a group either. They might not even know or like that someone. It doesn't quite fit in with what little I know about samurai virtues, and (at least in recent anime) the declaration's not limited to one gender.
Is there a term for this? Or a discussion of that trope?