Two Japanese boxers have died from brain injuries sustained in separate fights on the same event at Tokyo's Korakuen Hall. Shigetoshi Kotari, 28, collapsed shortly after finishing a 12-round draw against Oriental and Pacific Boxing Federation (OPBF) junior lightweight champion Yamato Hata on August 2.

He underwent emergency brain surgery for a subdural hematoma – a condition where blood collects between the brain and skull – but died on Friday.

"Rest in peace, Shigetoshi Kotari," the World Boxing Organization (WBO) wrote on social media. "The boxing world mourns the tragic passing of Japanese fighter Shigetoshi Kotari, who succumbed to injuries sustained during his August 2nd title fight.

On Saturday, 28-year-old Hiromasa Urakawa died after suffering the same injury during a knockout loss to Yoji Saito. He underwent a craniotomy in an attempt to save his life.

"This heartbreaking news comes just days after the passing of Shigetoshi Kotari, who died from injuries suffered in his fight on the same card," the WBO said in a social media post on Saturday. "We extend our deepest condolences to the families, friends, and the Japanese boxing community during this incredibly difficult time."

In response, the Japanese Boxing Commission has announced that all OPBF title bouts will now be shortened from 12 rounds to 10.

(With input from agencies)