Sakura Academy, nestled in a bustling city of nearly thirty million, boasts state-of-the-art facilities and a picturesque campus. Female students—succubi disguised as humans—can come and go freely, while male students are confined within its walls, permitted to leave only during holidays. Though marketed as coeducational, the truth is far darker: all teachers and female students are succubi, while only human boys, lured by rigorous entrance exams, are admitted.
Through deft information manipulation, the academy projects an image of a prestigious, disciplined private school, attracting earnest, high-achieving boys nationwide. But its true purpose is a sinister secret—a training ground where young succubi hone their skills in seducing and draining human males. The boys, unaware, are nothing more than captive "sustenance," farmed for the succubi's pleasure and power.