Pupa ( ピューパ) is a 2011–2013 Japanese horror manga series written and illustrated by Sayaka Mogi. An anime television series adaptation produced by Studio Deen premiered on January 9, 2014. The story of Pupa is about two teenagers, Utsutsu and his little sister Yume. Their father was an extremely abusive man, beating their mother and then his children after he was fired. After a divorce, their mother began dating another man, and the father left the two kids alone. Now orphaned, Utsutsu promised himself that he would always protect Yume.
After seeing red butterflies, these two siblings become infected with a virus known as Pupa. This virus mutates organisms into insatiable monsters, only seeking to feed on any sort of life. Yume succumbs to the full effects of the Pupa virus, but reverts into a human. Utsutsu, instead of turning into a monster, gains regenerative powers. In order for the virus to be suppressed in Yume, Utsutsu must take a drug and have Yume feed on his flesh.