Since giving birth to her only son Ataru, Yuu's husband has suffered from ED. For a long time, Yuu has been enveloped in loneliness and longing. Unable to forget this pain, she recently began repeatedly engaging in incestuous relations with Ataru. Unlike her husband, Ataru is young and possesses stamina so extraordinary it could be called "endless." Rather than satisfying her desires, Yuu's sexual appetite continues to grow more intense with each encounter.