Lee U was an ulzzang prior to debut. His father, Sul Woon Do, is a famous trot singer in Korea. Lee U first gained popularity in 2005 when he participated in many variety programs with his father. After the shot at fame, he was originally set to debut as a solo singer under the name U(唯). LeeU fell head over heels in love with music when he was studying in America from his 2nd year of Middle School to 2nd year of High School.