Master and Man (2019)

Taking its title—but not its plot—from a famous Tolstoy short story, Master and Man (2019) is a South Korean film about a couple who thinks that marriage will cure their individual needs for sex with multiple partners, but they soon discover that it's not quite that simple. Hyeon Dae (Lee Sang-won) loves his new wife Min Joo (Jung Da-won) and enjoys having sex with her, but he is quickly coming to the realization that one woman cannot satisfy his sexual urges and he is soon seeking multiple partners, many of whom are past sexual partners. Sadly, Hyeon Dae doesn't stray from heteronormative sex at all, but we do get some great looks at Lee Sang-won's bare ass in multiple straight sex scenes!