Tanaka entered Johnny's Jimusho in 1998 and made his debut with the group KAT-TUN in April 2011. However, his contract was terminated in September 2013 for his repeated violation of rules set by his agency such as engaging in music activities without permission. Since then, Tanaka has been the vocalist or rock band INKT which had just released its latest album "square" on 3 May. According to INKT's agency, the band and Tanaka himself will suspend their activities for the time being while investigations are underway. The band was supposed to be holding release events for the album such as at Aeon Mall in Suzuka, Mie, on 26 May and in the midst of its concert tours since 4 March. The 48 performances were supposed to be completed by July this year. All in-store events featuring the band at TOWER Records will also be cancelled.
Coincidentally, Tanaka had gone through a surprise urine test for stimulants last July on the BS Sky Perfect! TV programme "Tamura Atsushi no Chijouha de wa dame! Zettai!" where he was certified to be clean. This test was apparently initiated due to some tabloid reports then which hinted at Tanaka being a drug abuser thus leading to his friend Tamura suggesting the test to make things clear once and for all.
Sources: Nikkansports 1 / Nikkansports 2 / Nikkansports 3 / Sanspo / Yomiuri Hochi 1 / Yomiuri Hochi 2 / Yomiuri Hochi 3