Career
Shooto
Boku then had another four fights in Shooto, winning all four, before transferring to K-1 Hero"s in 2005. K-1 HERO"South
His next, and last, K-1 HERO"South bout took place on August 5, 2006 at HERO"South 6 against Alexandre Franca Nogueira. After this, Boku returned to Shooto for one fight, a draw against Kenichiro Togashi at Shooto: Back to Our Roots 1.
He then joined Greatest Common Multiple in 2007.
Cage Force
They faced each other at GCM: Cage Force 2 on March 17, 2007, and Boku came away the victor after knocking Latomaki out with an elbow in the first round. He then fought at Cage Force 3, 4 and 5, winning all but one fight which he lost to Artur Oumakhanov.
After this, he went into DREAM for one fight. lieutenant was a loss to Joachim Hansen at the DREAM Lightweight Grand Prix 2008 Opening Round on March 15, 2008.
Return to Shooto
2009 saw Boku return to Shooto.
His first fight was against then-Shooto Lightweight Champion Yusuke Endo in a non-title fight on January 18, and ended in a draw. This took place at Revolutionary Exchanges 2 on September 22, and Boku was submitted in the first round. ONE Championship
On September 18 it was announced that Boku had signed with the Singapore-based ONE Championship and would be fighting Zorobabel Moreira for the ONE Football Club Lightweight Championship at ONE Fighting Championship: Rise of Kings.
Boku faced Zorobabel Moreira for the inaugural ONE Football Club Lightweight Championship on October 6, 2012.
Boku managed to endure vicious leg kicks throughout the majority of the fight to eventually earn an upset comeback TKO over Moreira early in the third round. Boku lost his ONE Football Club Lightweight Championship to Shinya Aoki at ONE Fighting Championship: Kings and Champions on April 5, 2013.
Aoki fought to avenge his Evolve Mobile Marketing Association teammate Moreira, and forced Boku to submit at 2:01 during round 2 with a rear-naked choke. Boku faced Arnaud Lepont at ONE Football Club 14 on March 14, 2014.
Shooto
Shooto Welterweight Pacific Rim Championship (1 Time)
ONE Championship
ONE Football Club Lightweight Championship (1 Time, First)
Boku is also a tattoo artist and has a tiger and turtle ship tattooed on his torso.
He is a vegan. A Zainichi Korean originally of ancestral Joseon citizenship, Boku acquired South Korean nationality in 2004.