HANGZHOU, China -- Koo Bon-cheol brought South Korea its first gold medal in the martial art of ju-jitsu at the ongoing Asian Games on Friday, the high point of a career launched by an innocent mistake.

Now 26, Koo signed up for a membership at a local gym when he was 20, hoping to learn mixed martial arts (MMA) as a hobby -- except that the place wasn't teaching MMA.

"After a while, I realized the gym was specifically built for ju-jitsu," Koo said after capturing gold in the men's -77kg event at Xiaoshan Linpu Gymnasium in Hangzhou, China. "Now that I think about it, it was a pretty good stroke of luck for me."

Though Koo started out late, he made rapid progress in his new sport. Being trained in taekwondo also helped Koo.

"Because I didn't have as much experience as others, I figured I had to try two, three times harder than everyone else," Koo said. "I trained for more than eight hours a day."

As Koo started dominating domestic events and beating athletes from ju-jitsu powerhouse Brazil internationally, he emerged as a strong medal contender at the Asian Games. But Koo said he didn't really believe the hype.

"I asked myself, 'Will I really be able to win a medal here?'" Koo said. "I even felt afraid. I had to lean on people around me to regain some confidence before the final, and that led to such a great result."

After beating Ali Seena Ebrahim Abdulla Munfaredi of Bahrain by 4-1 in advantage scores, Koo said he wanted to thank one particular person -- his younger brother, Koo Bon-hwan.

"Since I got into ju-jitsu, he's been my sparring partner," the older Koo said. "I know I was really hard on him at times. I just want to say sorry, and I want to share this medal with him."

Koo also said his fiancee was on hand to root for him.

"We plan to get married next year, and this was a great wedding gift," Koo said. (Yonhap)