University student Shinji, who felt trapped in life because he couldn't make progress romantically or with finding a job, was given a chance to reincarnate. Moreover, he was given a "fated partner" to be with. He wondered if a happy life would begin, but then it began – an eternal death game where he must kill constantly, only ending when he finally is killed himself.

"Don't worry, Big Sis will kill you."

Joining the murder spree with "Sister" Hilde, who shows an unusual affection towards him...