Sakahira Riku, a first-year high school student, is jokingly pushed on the shoulder by his friend Tasaki while swimming by the pool, and falls into the pool with Mizumura Manami, who is next to him. The next day, when he wakes up, he finds that his body has been swapped with Manami's. Both are confused and try everything to get back to normal, but nothing works. They are forced to desperately exchange information about their families, friends, club activities, etc. in order to play the role of each other.
