Koki Tanaka (田中 聖, Tanaka Kōki) is a Japanese singer–songwriter and actor. He was a member of Jpop idol boy band KAT-TUN from their debut until September 30, 2013, when his contract with Johnny & Associates (the company that manages KAT-TUN) was terminated. When he was a member of KAT-TUN, he was recognized as the rapper in the group and has a hip-hop-influenced style. Out of the other members, Tanaka was most often paired up with Yuichi Nakamaru and they even formed a comedy duo 'TaNaka'. After leaving Johnny & Associates, Tanaka formed his own indie rock band called INKT.
Source: “Koki Tanaka”, English Wikipedia (CC BY-SA 4.0), excerpt