He began his career as a yakuza after graduating from middle school, when he met the head of the Suzuki-gumi, an Inagawa affiliate, in jail. He joined the Suzuki-gumi and founded a yamikin organization in Shinjuku, Tokyo, launching his underground financial business.[3]
He left the Suzuki-gumi in 1997 and along with his elementary school senior Yasuo Takagi, he joined the Shizuoka-based Mio-gumi, a tertiary organization of the Yamaguchi-gumi.[3]
In October 2002, following the retirement of the head of the Mio-gumi, Yasuo Takagi formed the Goryo-kai as the successor to the Mio-gumi. Kajiyama didn't join the Goryo-kai, retiring from the Yakuza world, but kept a strong connection with the Goryo-kai as the CEO of the Goryo-kai's underground finance ring.[3]
He was operating over 1,000 underground loan companies by August 2003, with estimated annual earnings of over $1 billion.[4] In August 2003 he was arrested for violating the investment law by "supervising moneylenders providing loans at unlawfully high interest rates".[2] He was convicted of 14 charges against him by 2005, and was sentenced to seven years in prison in February for money laundering involving the Standard Chartered Bank and Credit Suisse.[5]