Chi wa Mitsu Yori mo Amaku

Aki, a vampire, and his younger half-blood vampire sister Yura have lived together in a secluded forest for eighty years. Aki sustains himself by feeding on forest beasts, but a prolonged period without food leaves him weakened. Yura offers her own blood to save him.

The first time Aki drinks human blood, he loses control and rapes his sister. They both pretend it never happened, but the memory of that night lingers. As Aki grows weaker from refusing to feed, Yura insists he bite her again, even knowing the consequences. Aki warns her that if he does, he will do something even worse.