After his parents passed away, Koji started living with his brother and sister-in-law. His sister-in-law, Satoko, was dissatisfied with her husband Kazuichi's nightly activities. One day, the two accidentally opened a forbidden door... Koji's erect penis triggered Satoko's desire switch. She had a slender body and alluring lips... Could Satoko end that day's events as just a one-time mistake?
