ワタナベエンターテインメント
In October 2004, Kaji joined the Watanabe Entertainment group named the D-BOYS. As a member of the D-BOYS, Kaji also keeps a blog, which he updates occasionally. Being a part of the D-BOYS provided Kaji with a lot of opportunities. Among them was to perform with the group of boys and expand his experience as a performer. On August 6, 2005, Kaji, along with Hiroki Suzuki, appeared on the radio program, Marvelous Radio Vibration that was hosted by fellow D-Boys members Yuu Shirota and Kotaro Yanagi.