High schooler Gamou Shouya is a dead man-sort of. The real Gamou Shouya is long gone, but his body lives on, inhabited by the soul of a boy who made a pact with the succubus Armelina. In exchange for his services as her personal hitman, Armelina is helping him hunt down the people who brutally murdered him and his family. The path ahead is dark and deadly, but Shouya's got nothing left to lose... not even his soul.