At 1999's UFC 18, Kosaka returned to UFC fighting the legendary Bas Rutten in the first round of the "Road to the Heavyweight Title", which was a four-man tournament that would crown the next UFC Heavyweight Champion. Kohsaka dominated most of the fight with his superiority in wrestling and ground and pound, but ultimately lost by TKO when Rutten recovered in overtime and knocked him out with knees and punches. The fight was a source of heated controversy because referee John McCarthy seemed to unfairly stand the fight up when Kohsaka was mounted on Rutten and actively landing clean effective punches. This ordeal would be noted by Jake Rossen of "Black Belt" magazine, who wrote: "Overall, the event demonstrated an impatience for lengthy ground battles. Fighters were stood up after just a few minutes of grappling, in an apparent effort to maintain action in the matches. [...] This puts strikers, once the underdog of MMA competition, in a prime position to climb to the top."