Ohashi dropped out of college to begin a professional boxing career, and made his debut in February, 1985, with the Yonekura Boxing Gym. He won the vacant Japanese Light flyweight title in his 6th professional fight, and in December 1986, he challenged Jung-Koo Chang for the WBC Light flyweight title, but lost by TKO in the 5th round. Ohashi reclaimed the Japanese Light flyweight title in January 1988, and challenged Chang for the second time in June of the same year, only to lose again by 8th-round TKO. This was Chang's 15th consecutive defense of the WBC title, and Ohashi was knocked down a total of 7 times in 8 rounds before the referee stopped the contest. Ohashi challenged Jum-Hwan Choi in January 1990 for the Lineal and WBC Minimumweight title, and won by KO to claim his first world title. This win stopped the streak of 21 losses in a row suffered in world title bouts by Japanese boxers. There had been no Japanese world champions for over a year before Ohashi won the WBC title. Ohashi defended his title once, before losing to the legendary Ricardo López by TKO in the 5th round. López would go on to defend the WBC title won from Ohashi 22 times, and retire undefeated. After two years away from the world stage, Ohashi returned to fight WBA Minimumweight champion Hi-Yong Choi in October 1992. Ohashi won a unanimous 12-round decision to claim his second world title. He lost to Chana Porpaoin in his first defense, and was forced into retirement at the age of 27, after it was discovered that he had a detached retina. He ended his career with a record of 19-5-0.
Post-retirement
After retiring, he created the Ohashi Boxing Gym in his hometown, Yokohama, and currently works as a trainer there. Former WBC Super flyweight champion, Katsushige Kawashima, is trained by Ohashi. In January 2007, Ohashi served as the head trainer of the Japanese team in the BOXING GRAND PRIX 2007 event. He also serves as the president of Japan Pro Boxing Association and its subsidiary body East Japan Boxing Association.
