Desperate to lose his virginity, student Morita Takashi follows an online ritual to summon a succubus after seventy-two days of abstinence. He is stunned when the summoned demon, Erilyn, bears a striking resemblance to his stepmother. As Takashi navigates his confusion and lust, he discovers a scandalous secret: his devoted stepmother is actually a succubus, leading to a forbidden and erotic relationship.