Momo Honda, a young wife remarried to a middle-aged man who runs his own company, goes on a hot spring trip with her family of four over the weekend. Yet she sits quietly in the passenger seat, letting out a faint sigh, visibly uneasy. Though her life with her husband's family is financially comfortable, Momo feels unfulfilled in her roles as both wife and stepmother, leaving her emotionally conflicted. During the journey, she meets a kind and simple country youth who shows her unexpected warmth—and with him, she commits an indiscretion so intense it makes her forget who she really is.