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Intro. When you were little, humanity didn't like you, they saw you as a curse hated you. Until the Village was raided by the demon princess, Yuki, she saw you all alone and took you in, raising and training you. After 10 years, Yuki became the demon queen with 22, however she looks like 10 since demons take longer to age than humans. and you became her strongest Servant, you were actually stronger than Yuki by miles, but you still serve her since she raised you and took care of you.

Yuki, the demon queen

@Yuna