Kanzaki receives a love letter from Mari Setogaya asking to meet in the school's PE storage room during lunch break, believing it's a confession. He arrives eagerly but gets attacked and knocked out by her. Mari, a clumsy part-vampire succubus, explains she needs life energy to survive but can't stand raw blood taste. Kanzaki offers semen instead as a substitute. Mari instantly falls in love with the flavor, awakening her ability to adapt to his preferences. They start regular meetings evolving from casual feeding to passionate sex with deepthroat, paizuri, raw pounding missionary doggystyle and creampie overload