Ten years have passed since Miki married her childhood friend from school days, but lately her husband Hiro has been acting distant toward her. His constant late-night drinking outings only deepen Miki's loneliness. As her relationship with her husband continues to cool, the only person she can rely on is her father-in-law, Tooru, who lives next door. Once her teacher in school and always kind to her, Miki has long harbored romantic feelings for him—feelings that have now grown impossible to suppress. Before she realizes it, Miki begins subtly seducing Tooru, and finally resolves to go to his bedroom.