Since childhood, Mako has harbored a secret fascination with her anus. One day, introduced by her mother, she meets her uncle and confides in him about her sexual desires. Their conversation quickly spirals into a lewd relationship. Mako experiences new pleasures—outdoor blowjobs, drinking urine, and the intense sensation of having her anus licked and penetrated by his tongue. But the relationship between her and her uncle goes beyond mere blood ties; in truth, he's been having an affair with her mother. Driven by a desire to surpass her mother, Mako offers her anal virginity and golden shower to her uncle. By willingly accepting his feces into her body, she crosses a new boundary into ultimate submission.