Seven years into her marriage, housewife Miho lives a quiet life with her salaryman husband. One night, her husband brings home a friend named Yamashita, a mutual acquaintance from their student days whom Miho already knows. Yamashita suggests a drink with her husband, who's been busy lately, and Miho warmly joins in, attentively engaging with their guest. Yamashita proudly shares that he's recently started working out at the gym, showing off his newly built muscles. With a grin, he says, "Miho-chan, go ahead and touch," as he begins unbuttoning his shirt. Amid this casual exchange, their relationship takes an unexpected turn.