Koichi's best friend, Igami, witnessed his mother, Rinko, secretly meeting with a younger man at a love hotel in Shibuya. He revealed the incident to Koichi over the phone, shocking him deeply and forcing Koichi to confront his own subconscious attraction toward his mother as a woman. The next day, Igami visited Koichi's home, exposed the affair, blackmailed Rinko, and demanded sex. When Rinko submitted to his demands, Koichi arrived at the scene, triggering a bizarre threesome.