Below is the translation for the announcement posted on Johnny's net website.
"We have decided to cancel our exclusive contract with KAT-TUN's Tanaka Koki as of September 30th, due to his repeated violation of the company rules. KAT-TUN will continue their activities with 4 members after Tanaka's withdrawal, so we would like to ask the fans for your support as you have done until now. - 2013.10.9 Johnny & Associates, Inc."
"It is what the company's announcement says. I told the members my gratitude for being in the group with me though I have caused so many troubles until now, and my feeling of apology that I am sorry. I am planning to continue my activities, so I will make further announcement when the details are set. - 2013.10.9 Tanaka Koki"
"To our fans and people concerned, we are terribly sorry for causing trouble this time. In order for us to raise the group's consciousness, we have had many talks, but we are very disappointed that it ended up like this for our member who we have been together for over 10 years. From now on, KAT-TUN's activities will continue with 4 members, so please continue to support us. - 2013.10.9 KAT-TUN"
Source: Johnny's net website