Sunao Akiyoshi never recovered from being cheated on by his middle school girlfriend Lemon Nishikawa, but he has finally developed feelings for Natsumi Kogahara in his college film club. Then Lemon reappears. The next morning, Sunao wakes up inside Lemon's body — and she finds herself inside his — caught in an involuntary body-swap that forces both of them back into each other's daily lives.