A Beautiful Moment (2018)

An ageing bachelor playboy finally meets the girl of his dreams and proposes marriage, only to discover her psychologist stepmom was his first love long ago. The future in-laws initially pretend not to know each other but as the wedding date gets nearer, the rekindling of long-dormant feelings develops into a cross-generational love triangle. My Rival is Son-in-law, My Lover is Son-in-law