Due to her son's strong desire to enter graduate school, Tsubaki visits the home of her sister Chiaki and husband Arisue. She pleads intensely, "I will take full responsibility for covering all of my son's tuition and living expenses." Chiaki owns a shop in Ginza and performs BDSM shows for regular customers. To prepare Tsubaki for the show, she is first trained as a female dog. On the fateful day, Tsubaki encounters her son, brought along as one of the guests by her uncle Arisue. Eventually, amid humiliation and degradation, mother and son are forced into sex.