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.