Rei and Tetsugaku are childhood sweethearts and husband and wife. They've been married for five years and seem to be as close as ever, but this summer, Tetsugaku finds out he's been cheating on her. They can't have a baby, and Rei is in the depths of despair. Meanwhile, Tetsugaku's father, Dango, is staying at their house on a business trip to Tokyo. Rei is reunited with Dango, who was always nice to her when she was in her hometown, and she is drawn to him. When she realizes that she has been subtly seducing Dango, she makes up Kokoro and heads to Dango's house...