KAT-TUN (カトゥーン, Katūn) is a Japanese boy band formed under Johnny & Associates (Johnny's) in 2001. The group's name was originally an acronym based on the first letter of each member's family name: Kazuya Kamenashi, Jin Akanishi, Junnosuke Taguchi, Koki Tanaka, Tatsuya Ueda, and Yuichi Nakamaru. Their debut on March 22, 2006 was marked by a tripartite release of a CD single, album and music DVD on their exclusive record label J-One Records. Since then, all of their single, album and music DVD releases have debuted at number one on the Oricon music and DVD charts.
In 2010, Akanishi left the group to start a solo career, making the group's acronym then come from KAmenashi, Taguchi, Tanaka, Ueda, and Nakamaru, and the group toured with five members. In 2013, Tanaka's contract was terminated for several violations, leaving KAT-TUN as a four-man ensemble, and Tatsuya Ueda took the T to keep the acronym. By the end of March 2016, Taguchi left both the group and the agency, leaving KAT-TUN with only three remaining members.