One day, Ichigotani Nanako is taken aback when she receives an unexpected confession from Agasa Yuki, the brilliant prince at her school who is also her junior in the club. Caught off guard, the naturally airheaded Nanako accidentally exclaims, "I''ll be in trouble if you die though!" and ends up entering a relationship with Agasa-kun. Regardless, Agasa-kun has an intense obsession and possessiveness, showing no mercy to any bugs that approach Nanako!