Kazuyuki, Fumio, and Sara used to teach at a rural school. At that time, there was talk of an assignment to Tokyo, but his father, who was sick, was worried about Kazuyuki, and Fumio was assigned instead. And Kazuyuki and Sara, who escaped assignment, get married. ... Since then, he has been estranged from Fumio, but when he contacted him for the first time in a long time, he said that he fell ill and retired. Kazuyuki and Sara invited Fumio to their home. Fumio approaches Sara to take advantage of Kazuyuki's absence.