Despite carrying injuries from his grueling year schedule, Kosaka also took part in the second UFC event in Japanese soil, UFC 23, where he was pitted against Ruas Vale Tudo exponent Pedro Rizzo. The two contenders spent a round cautiously, until Rizzo switched to aggressive leg kicks and Kohsaka tried to take him down in return. Through the match, Pedro blocked TK's efforts to get it to the ground and landed more punches and leg kicks. After Kohsaka had absorbed a long punishment, Rizzo landed a right punch for the TKO.