Shirai first boxed in elementary school, during a mock match-up against a kangaroo at a local carnival.

Shirai's boxing skills improved dramatically under Cahn's guidance, and the two formed a close bond.

Cahn made Shirai live in his house, and supervised everything from his health and training to his meals.

Shirai lost by split decision but fought Marino again in December, 1951, to mark a 7th round KO win.

Shirai worked as a boxing commentator and critic before creating a sports gym in 1995 with former world champion Yoko Gushiken.