Yuko Ishibashi lives alone with her son Ryota, a college prep student, while her husband works in another city. Cheerful and dependable, she had been enjoying a peaceful life—until one day, her husband's junior colleague, Oshima, visits and reveals that her husband has been embezzling funds. Yuko refuses to believe it, insisting her honest, hardworking husband would never do such a thing. But when she loses contact with him, his calls stop, and even his meals become scarce, her anxiety grows. To cope with the emotional void, she turns to masturbation, losing herself in self-pleasure. Meanwhile, Ryota, who has always seen his mother as upbeat and strong, begins to sense something is off—her usual demeanor now feels forced, and he starts to suspect that things at home are not what they seem.