Their first hit was the song "너만은 모르길" (Only You Wouldn't Know), released in 1999 by Rock Records. Between their fourth and fifth albums, their contract with Rock Records expired and they signed with EMI Music Publishing Korea; a label which also manages other K-pop stars like DJ DOC and Baby V.O.X..
In late 2006, As One released their fifth album 12 Tears of Farewell, and started their promotional activities with the lead track "십이야" (12 Nights).
They are currently under the management of Brand New Music and they host a radio show called K-Popular on TBS eFM radio.
In contrast to their usual style, As One released a 19+ rated music video ahead of their October 29, 2014 release date for the single "오늘같은 날" (For the Night). The music video featured labelmate Jae Woong from 4-member hip hop group Troy and fitness model Kim Hae Na.
Crystal (Chae Da-hee 채다희), is from Los Angeles, California, where she attended Chatsworth High School. On September 16, 2012, Crystal married her former manager, Cho Min Chul, after ten years of dating. Crystal announced her 5-month pregnancy on October 18, 2013, and in March 2014 her agency, Brand New Music confirmed that she gave birth to a son.
Min (Lee Min-young 이민영) was born in Seoul, South Korea but attended high school at Fairfax High School in Los Angeles, California. On November 29, 2013, Min married her boyfriend of two years in Hawaii. Min composed and co-wrote the lyrics for the song titled "2=1" from As One's album Simply As One for her husband.