Yoshimura Sumomo: Dorei ningyô (2001)

Aki leads an ordinary married life with her husband, Kai. One day, she receives an email asking, "Why not put your body up for auction?" If a buyer is found, she is contractually obligated to serve as a sexual partner for the duration of the agreement. While Kai is away on a business trip, Aki visits the venue. Stripped naked and subjected to various examinations, she is bombarded with questions from potential buyers. Ultimately, a man named K wins the bid at a high price. He "trains" her using bizarre methods—such as forcing her to record videos of her private life and her sexual encounters with her subordinate, M—awakening a side of her body that her husband had never explored...