Pupa

Utsutsu has long tried to shield his younger sister Yume from the violence of their home. Their dependence on each other takes a terrifying turn when an encounter with red butterflies is followed by a mysterious infection.

Yume begins transforming into a creature driven by an uncontrollable hunger, while Utsutsu develops extraordinary powers of regeneration. Determined not to abandon her, he becomes caught between protecting other people and sustaining the sister he loves. A researcher named Maria offers knowledge of the virus, but understanding it does not make the siblings' ordeal any less frightening.