In the judo-focused Yamashita household, the family's strict daily training regimen reflects their disciplined lifestyle. However, beneath the surface of this seemingly harmonious family, Yayoi is entangled in a secret lover's relationship with her stepbrother while covertly securing funds to keep the dojo running—all hidden from the rest of the family. One day, noticing that her training focus is slipping, Yayoi confronts him, and for the first time, the virgin Takeshi confesses his long-suppressed feelings for his mother, Yayoi. Initially guiding him as a mentor to help him become a man, Yayoi gradually begins to develop deeper, conflicted emotions toward her son, causing her to question her ongoing affair with her stepbrother. Caught between family duty, desire, and morality, a complex web of human relationships unfolds.