Love Hunter (1972)

Twenty-year-old Kazuo is in love with his college girlfriend, Hisako, but he can't help but be intrigued by a mysterious older woman named Kyoku, a promiscuous woman unsatisfied with her marriage. As time goes on, both Kazuo and Hisako are pulled into the seemingly rules free, borderless world of Kyoku - with all of its many pains and pleasures.