Junto Nakatani hopes to get a close look at Naoya Inoue after he fights on his countryman’s undercard December 27.

If Inoue and Nakatani win their junior featherweight fights, they’re expected to meet in what would be the biggest all-Japanese showdown in their country’s boxing history sometime in May at Tokyo Dome. Watching Inoue perform from a ringside seat inside Mohammed Abdo Arena in Riyadh, Saudi Arabia, is as close Nakatani will have come to getting in the ring with him until they fight.

That’s because Rudy Hernandez, Nakatani’s longtime Los Angeles-based trainer, instructed the former Ring/IBF/WBC bantamweight champion to avoid sparring with Inoue because he was sure that they would fight one day. Nakatani has sparred with Inoue’s younger brother, newly crowned WBC bantamweight champ Takuma Inoue, but he has only spoken briefly with the undisputed 122-pound champion.

“Rudy told me not to spar with him,” Nakatani, a southpaw, told The Ring’s Mike Coppinger. “We were conscious of it.”

Nakatani (31-0, 24 KOs) has moved up from the bantamweight limit of 118 pounds to 122 to meet Mexico’s Sebastian Hernandez (20-0, 18 KOs) in the 12-round co-feature of “The Ring V: Night of the Samurai” card. Inoue (31-0, 27 KOs) will defend his Ring, IBF, WBA, WBC and WBO belts against another Mexican, Alan Picasso (32-0-1, 17 KOs), in the main event of a DAZN Pay-Per-View show ($39.99 in the United States; £19.99 in the UK).

Nakatani, 27, acknowledged there is a lot at stake on a card that will feature at least one Japanese boxer in each fight.

“I realize that it’s a fight that everybody wants to see,” Nakatani said of facing Inoue, “and that’s a source of motivation for me.”

Inoue, a four-division champion, is third on The Ring’s pound-for-pound list, four spots above Nakatani, who has won world titles in three weight classes. Sebastian Hernandez isn’t nearly as accomplished as them, yet Nakatani knows his unbeaten but unproven opponent could ruin a huge fight that has fascinated fans worldwide, not just in Japan.

“There’s obviously business that we have to take care of first,” Nakatani said. “We have to win this fight, but one of my goals is to give a performance that will make people more excited about the fight in May.”