Of the two men it's Ono who is the more well known. He's a former OPBF Light Flyweight champion, having won that title back in 2013, he has twice fought for world titles, losing to Katsunari Takayama and Knockout CP Freshmart, and come up short in 3 Japanese title bouts, losing to Kenichi Horikawa and Reiya Konishi and fighting to a draw with Tatsuya Fukuhara.
At his best Ono was a skilled boxer-mover, and he holds notable wins over Yu Kimura, Xiong Zhao Zhong and Omari Kimweri. Sadly however he is now 35 years old, ancient for a Minimumweight, and with 203 rounds under his belt he has taken a lot of punishment. That has included 3 stoppage losses, with the most recent coming in 2015 to Kenichi Horikawa, and a lot of other accumulative damage from tough fights with Konishi, Knockout and Takayama. What hasn't helped has been his lack of power and despite scoring stoppages in his last 3 wins they have come against frankly terrible opposition.
We know Ono will be hungry, with this almost certainly being his final chance to claim a Japanese title but he has a lot of things going against him here, including his age, wear and tear and generally lacking the power he'd need to get the respect of any decent domestic opponent.
Whilst Ono has been fighting at title level for years the same can't be said of Hirai, who will be fighting in his first title fight here. The 27 year old from Kobe made his professional debut in late 2011 and struggled to find his groove, going 3-3-1 in his first 7 bouts as he bounced from Minimumweight to Super Flyweight. Following 3 successive losses he returned to Minimumweight and rebuilt his career by winning 7 of 8 bout. Those wins have shot Hirai up the Japanese rankings and have included recent victories over Takimi Sakae and Ryoya Ikema, which have helped him break into the WBO top 15 and earn this title fight.
Although relatively unknown we have been impressed by what we've managed to see of Hirai. That included his win over Ikema in which Hirai showed good composure when Ikema looked to him out early, smart movement, a good judgement of distance, lovely speed and some very sharp punching, especially to the body. Those are tools that he will be looking to use against Ono, who like Ikema is a southpaw.
Whilst this is a slight step up in class for Hirai, following his wins over Sakae and Ikema, it's hard to imagine his current 5 fight winning streak coming to and end to Ono, who has looked like a man on his way down for a while. Ono won't be there to lose, but we suspect Hirai will have a bit too much of everything for the veteran, and will score a late stoppage of Ono to send the Watanabe man into retirement.