My Stepmom Is So Much Better Than My Wife... Hana Haruna(2022)

After being rejected by his wife when he tries to initiate intimacy, a man finds himself alone with his attractive mother-in-law who has come to visit. Unable to take his eyes off her, he later discovers her underwear in the bathroom and gives in to temptation. When she walks in on him, she decides to keep it a secret for the day and takes things further herself, leading to a forbidden affair that proves far more satisfying than his marriage.