The southpaw, who captured WBC belts from bantamweight to featherweight from 2005 onwards, has now relinquished the World Boxing Council super-bantamweight championship with immediate effect.
“I’ve decided to retire with the Sept. 16 bout being my last, when I conquered my third division,” Hasegawa said at an arranged press conference. “It was a boxing career that had more than I expected.
“I’ve always imagined hanging up my gloves as the world champion. It’s like with eating; you have to stop when you are not quite full.”
Head of Shinsei Gym, where Hasegawa trained, Masato Yamashita added: “I’m happy it didn’t end with him balling his eyes out, he can leave as the world champion. I’ve been telling him to decide however he likes. I’m half-sad, half-relieved.”
Hasegawa concluded: “I’ve got no reason to fight on. I made the decision thinking this might be the best time to do so. I can still get up physically but mentally it’s been getting difficult.
“I’m proud. I’ve had a career that couldn’t have been any better. Now, I’d like to find a new stage on which I can fight.”
The pound for pound rated star leaves the sport with a record of 36-5 and three wins on the spin, having recently defeated Hugo Ruiz to claim the third and final world title of his distinguished career.