Succubus and Hitman

High school student Gamou Shouya is a mere vessel, housing the soul of a youth who teamed up with a succubus named Armelina. The original Shouya Gamou is long gone, a victim of a brutal massacre that also claimed the lives of his loved ones. Armelina has promised to assist him in taking revenge against their attackers, but only if he acts as her personal assassin. With nothing left to lose, not even his soul, Shouya remains undeterred in the face of danger and uncertainty.