花火与小爱在旁人看来就是一对理想中的情侣，但实际上两人只是为了无法实现的恋情而烦恼的契约爱人，并过着将对方当做所爱之人，互相感受温暖的日子。不断为了重要的人而感到受伤的青涩青春模样，比谁都更加单纯却更加扭曲的爱情故事。

High schoolers Mitsuha and Taki are complete strangers living separate lives. But one night, they suddenly switch places. Mitsuha wakes up in Taki’s body, and he in hers. This bizarre occurrence continues to happen randomly, and the two must adjust their lives around each other.