Madoka lives with her husband and father-in-law. His father-in-law, whose hobby is shogi, puts up a condition that he should take off Madoka's clothes if he loses in order to play against his rival shogi opponent, Isoyama. And Madoka, who has been humiliated in front of her father-in-law, gradually becomes absorbed in sexual intercourse with an old man and develops into a physical relationship with her father-in-law.