The daughter of the demon king, Kagura Itsuki, leads an ordinary life in the human world while hiding her identity. She attends middle school and spends her days with three childhood friends who are also魔族 (demon race) boys: Moon Island Mio, a werewolf with a straightforward and jealous personality; Tachibana Ryuji, a strong and protective oni; and Kurozaki Touya, a clingy, sweet-natured vampire who is active at night and weak to sunlight. Just before her fourteenth birthday, Itsuki's father, the demon king, gives her a ring meant for a fiancé, revealing that her three friends are actually her fiancé candidates. She must choose one of them as her future husband.

Itsuki, who has never thought of them romantically, struggles with the pressure. Meanwhile, the three boys take the competition seriously, each trying to win her heart through various romantic schemes and acts of devotion. The story follows their daily lives as they navigate school, misunderstandings, and magical mishaps, such as a love potion incident, a shared tent during a camping trip, and a memory-loss arc where Itsuki forgets the boys entirely. New rivals appear, including a tengu named Amami and a snake clan member named Kano, who test the boys' determination. The narrative deepens as the boys' past with Itsuki is revealed, and their feelings intensify, leading to moments of jealousy, protectiveness, and heartfelt confession. The series blends fantasy romance with light comedy, set against the backdrop of middle school life in the human world.