Yuji Takanashi is a university philosophy professor who can't swim. Making awkward justifications to himself about the relationship between water and people, still he decides on the spur of the moment to enroll in a swimming class. There he encounters the teacher Shizuka Usuhara, who ignores his last-minute hesitation and enrolls him.
Atsuhisa Yamada is an ordinary man, with a wife and a 5-year-old daughter. He is close to his childhood friend Takeda. One day, Atsuhisa Yamada leaves his office during work hours and goes back home early. There, he witnesses his wife and an unknown man having sex, but Atsuhisa Yamada is unable to express his feelings like anger, frustration, and depression. His relationship with his wife and his friend Takeda becomes distorted.