Two years ago, Yayoi Yanagida accidentally discovered her stepson Taichi engrossed in masturbation, which led to the beginning of a sexual relationship between them. Their affair continued, and Yayoi cherished each day she spent with Taichi. One day, the two set off on a trip together, just the two of them. Yayoi had intended to end their relationship during this journey, but unexpected events threw her plans into chaos.