The Korean Top Team, Geun Ho Son, prospect entered Bangkok with momentum, but Ryoto Nishiyama brought his ONE Championship debut to a sudden end.
Just seven weeks after scoring a first-round finish of his own, Geun Ho Son found himself on the other side of one.
The 27-year-old Korean prospect made his ONE Championship debut at ONE Friday Fights 168 on August 28, 2026, but his introduction to the promotion ended in a first-round knockout loss to Japan’s Ryoto Nishiyama at Lumpinee Stadium in Bangkok, Thailand.
Nishiyama landed the decisive left hook late in the opening round, knocking Son out and forcing referee Mohamad Sulaiman to stop the fight at 4:36.
It was a difficult result for Son, who entered his ONE debut carrying some momentum.
On July 11, Son stopped Nadir Dosimbetov with ground-and-pound in the opening round, giving him a statement victory shortly before making the jump to the ONE Friday Fights stage.
Several outlets also favored Son entering the matchup with Nishiyama.
Instead, it was the Japanese fighter who stole the spotlight.
Nishiyama remained dangerous throughout the opening round before finding the punch he needed in the closing seconds. His left hook ended the contest emphatically and turned his own ONE debut into a memorable one.
The finish also earned Nishiyama a 350,000 baht performance bonus from ONE Championship CEO Chatri Sityodtong.
For Son, the loss drops his professional record to 5-2-1 and puts a temporary halt to the momentum he carried into Bangkok.
But at 27 years old, this doesn’t have to define his ONE Championship run.
Son represents Korean Top Team and arrived in ONE as a developing prospect rather than a finished product. His previous performances have already shown his ability to finish fights, particularly when he can impose himself offensively and bring the action to the ground.
Nishiyama provided a very different lesson.
At this level, one defensive mistake can erase everything that came before it.
After competing twice in less than two months — and suffering a definitive knockout in the second appearance — the immediate priority for Son will be recovery before returning to training and addressing what went wrong in Bangkok.
Where ONE Championship goes with him next remains to be seen.
A debut loss can change the trajectory of a prospect, but it doesn’t have to end it. Son is still only 27, still relatively early in his professional career, and now has something he didn’t have before August 28:
Experience on the ONE Championship stage.
His debut didn’t go according to plan.
What he does with it may tell us considerably more about Geun Ho Son than a win would have.
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