Yun Seo Bin was a Korean pop trainee for one year and seven months under JYP Entertainment prior to his appearance as a contestant on boy group survival reality show Produce X 101. After the first episode of the show was aired, he removed from JYP Entertainment and Produce X 101 due to the rumors claiming that he was involved in severe bullying, underage drinking, and underage smoking when he was in elementary and middle school. He has apologized for the controversy surrounding his past ignominious actions through a handwritten letter of apology that he posted on Instagram.