18 Again

Jung Da-jung (Kim Ha-neul) and Hong Dae-young (Yoon Sang-hyun) are married and have a set of fraternal twins, Hong Shi-ah (Roh Jeong-eui) and Hong Shi-woo (Ryeoun). At first, they have a perfectly happy marriage despite having children at a very young age and having financial problems. Years later, their happy marriage starts crumbling when 37-year-old Da-jung files for divorce and their 18-year-old good looking twins start ignoring Dae-young, except for pocket money. Furthermore, Dae-young's life turns more miserable when he loses his job, after his boss promotes his nephew who has worked in the company for only 4 years, while relocating Dae-young to Busan. Wishing he could go back in time and fix his life, Dae-young's 37-year-old body miraculously morphs into the body he had when he was 18 years old (Lee Do-hyun) but retains his 37-year-old mentality. He starts living a new life under his alias "Go Woo-young" and attends Serim High School, which is his twins' school, and also the school he and Da-jung attended 18 years ago. During Dae-young's life as the 18-year-old Go Woo-young, he learns that his daughter Shi-ah is working part-time in a convenience store without his permission and his son Shi-woo is being bullied at school by the basketball captain, Goo Ja-sung (Hwang In-youp). Dae-young also learns about his son's interest and talent in basketball that Shi-woo always hides from him. Dae-young eventually realizes the true reason behind his family's crumbling bond and gets to know more about his twins. He resolves to use this chance to protect his kids by befriending them and doing his best to be more present to the family despite his appearance as an 18-year-old boy.