Aoi Okana, 40 years old. She's a mother of one, and has maintained her perfect H-cup figure with a slender waist, hard to believe she's a housewife. Married for 16 years, she still maintains that figure. As she ages, her mature allure grows stronger, but her anxious husband restricts her, confining her to the house and keeping her like a birdcage, even though she wants to work outside. Despite this, her husband comes home late, and their nighttime activities have decreased year by year... Aoi, who has always been laid-back and not assertive, finally explodes with years of stress. "We had our first fight as a couple." Her libido, no longer controlled by masturbation alone, sparks a desire to cheat, opening the door to her first infidelity in her 40s.