Sun and Nuea are dating, but Sun realizes that something is wrong with his 'physiology', so he quickly confides in his friend Third, who takes out a soap with magical effects and asks him to use it when taking a bath. Sun does so, but unexpectedly, Nuea suddenly joins him in the bath, and when he wakes up the next day, they actually exchange souls! They go to Third for help again, but a problem emerges.