The loss, however, was instrumental in Kohsaka's career, as it made him close friends with Frank Shamrock and Maurice Smith, who became his training partners in the team The Alliance shortly after. In April 1999, after a series of matches in UFC, Kohsaka fought Dutch kickboxer Gilbert Yvel in RINGS. The match saw a worn Kosaka getting ahead in points by multiple fouls from Yvel, but he failed at submitting him while Yvel landed several knockdowns, until one of them caused the fight to be stopped. They rematched in August, when an improved Kohsaka immediately threw Yvel down, hit him with numerous body punches and submitted him with a toehold for a rope escape; however, the bout was interrupted for Kohsaka falling out the ring in another hip throw, getting injured. As TK had scored a point before the bout went to no contest, the match was counted as a victory for him. Finally, Yvel and Kohsaka had a rubber match during the King of Kings Tournament, but it was short and uneventful, as TK was stopped again by a bleeding cut. In August 2000, TK faced the King of Kings semi-finalist Antônio Rodrigo Nogueira. Started the fight, Kohsaka blocked a takedown and transitioned it into an uchi mata, but Nogueira pulled him to the ground and mount him. The judoka escaped from under him, only for Nogueira to regain position, but this time it was Kohsaka who reversed him into a leglock attempt and pressed into his guard when it failed. At the next round, Kohsaka stopped another takedown with a leg hook tawara gaeshi and continued pressing, blocking Nogueira's attempts to work submissions from the bottom and striking when possible. Nogueira mounted him again and threw punches, but Kohsaka performed again his signature escape into leglock and keep attacking his guard. A pair of sweeps later, Kohsaka controlled position until the end of the time. The match was ruled a draw. During the next King of Kings tournament, Kosaka advanced over Mikhail Ilyukhin by knockout and Mikhail's teammate Fedor Emelianenko by doctor stoppage. The latter was again a controversial technical victory, as the cut was caused by a missed looping punch where Kosaka's elbow struck Emelianenko's head, reopening a cut sustained in his previous fight against Ricardo Arona. Since the fight was in a tournament format, a winner and loser were required because draws and no-contests were not