Yukari lives with her husband and son Tsuyoshi, and it has become her daily routine to wake Tsuyoshi up every morning. Recently, as temperatures have risen, it's become harder for him to wake up to his alarm, making her morning wake-up calls a regular habit. One morning, while reaching over to turn off the alarm in his place, Yukari's hand accidentally brushes against Tsuyoshi's morning erection. In that instant, she becomes aware of her own body pressing against his, and despite knowing it's wrong, she begins moving her hips on her own, seeking pleasure. From that day on, her heart changes completely. She becomes obsessed with the cowgirl position—a role where she takes control and moves freely as she pleases. A new chapter of her life begins.