[1][2] By at least late 1990, he was directing adult videos for the HRC Cher label, including The Female Teacher's Nightmare Trap 4.
"[6] In addition to adult videos, Kaji directed the Hot Pictures V-Cinema production Nippon saikyou no seiyoku sha (日本最強の性欲者), which was released in October 1996[7] In July 1997, Kaji produced and Hot Entertainment released another V-Cinema title, Juvenile Crime (少年の犯罪, Shōnen no hanzai), starring Yumi Yoshiyuki and directed by Gunji Kawasaki, with a story based on a real murder case.
"[13] He was also the executive producer for the Hot Entertainment March 2000 production of screenwriter Toshiyuki Morioka's debut as a director, Requiem of Darkness (クラヤミノレクイエム, Kurayami no rekuiemu).
[17] Kaji has also been involved in other business ventures, including the video production company Hot Pictures (ホットピクチャーズ, Hottopikuchāzu),[1] the retailer Hot Powers (ホットパワーズ, Hottopawāzu)[1] with shops and a website selling adult toys and sex aids,[18] and Japan Entertainment Co. Ltd. (有限会社ジャパンエンターテイメント, Yuugen Kaisha Japan Entāteimento)[1] In 2005, he established Tigermeisters (タイガーマイスターズ, Taigāmaisutāzu),[1] a production company which specializes in adult videos featuring transsexual actresses, including AV Idols Miki Mizuasa and Hime Tsukino.
[19] Kaji has also worked as a photographer and stylist, and, in January 2009, he published his first novel, entitled Shinya no teiou (深夜の帝王) (ISBN 4286045196).