After graduating from Tokyo Korean Junior and Senior High School, he made his professional debut in 1994, and challenged the Japanese Flyweight Title twice in 1997, but was unsuccessful both times.
He defended his WBC and lineal super-flyweight titles eight times before suffering a stunning first-round knockout loss to Katsushige Kawashima in 2004.
Tokuyama was knocked down in the last round, but dominated Kawashima for the rest of the fight, regaining his title by unanimous decision.
He has often taken politics inside the ring, carrying a North Korean flag in his entrances and wearing trunks labeled "One Korea."
News of the kidnappings received huge media coverage in Japan, and Tokuyama's website was spammed relentlessly with abusive messages when it was rumored that Tokuyama commented: "They (the kidnapped Japanese citizens) might actually be living pretty happily in North Korea.