The fight will mark the third straight trip to Japan for Puerto Rico’s Santiago, 15-4 (9 KOs), though he certainly isn’t complaining. A 33-year-old from Humacao, Santiago enjoyed a career-best year on the road in 2025, dethroning reigning titleholders in back-to-back fights.

His first came in a stunning 12-round unanimous decision victory over Shokichi Iwata to earn the WBO 108lbs belt last March 13 at Ryogoku Kokugikan Sumo Arena in Tokyo. Iwata was heavily favored, but Santiago’s relentless work rate was more than enough to sway all three judges. 

Santiago returned to the famed Kokugikan for an encore performance, his WBA title-lifting effort over unbeaten Kyosuke Takami. Their December 17 unification bout saw Santiago prevail via split decision to extend his current three-fight win streak.

“El Chulo” Santiago is one of four current titleholders for Puerto Rico. Interestingly, all four are not only unified champs but also hold both the WBA and WBO belts at their respective weights. Oscar Collazo is the unified, lineal and Ring champ at 105lbs; Xander Zayas is a two-belt titleholder at 154lbs; while Amanda Serrano – the island’s first-ever undisputed champion – remains the unified, lineal and Ring queen at featherweight. 

On the other side of the equation, Taniguchi hopes to become a two-division titlist with this opportunity.

Taniguchi, a 32-year-old, Tokyo-based southpaw, held the WBO 105lbs title for more than a year before he suffered a crushing second-round knockout defeat against Melvin Jerusalem atop a January 2023 card in Osaka. Taniguchi then rattled off a three-fight win streak before suffering a 12-round split decision to Thailand’s Thanongsak Simsri, 39-1 (34 KOs), in their December 2024 title eliminator.

Simsri went on to claim the vacant IBF 108lbs title in a split decision victory over Cristian Araneta last June 19 at Ota-City General Gymnasium in Tokyo.

Meanwhile, Taniguchi punched his way back into contention with two knockout victories in 2025. In his most recent outing, he stopped Takeru Inoue (no relation to Naoya or Takuma) in the fifth round last August 3 in Osaka.

There were earlier whispers that Santiago would next face Daiya Kira, the fast-rising junior flyweight and current WBA No. 1 contender. The bout was targeted to land on the undercard of the yet-to-be-announced (or confirmed) Naoya Inoue-Junto Nakatani superfight in Tokyo.

BoxingScene has learned that Santiago-Kira is still very much in play but likely to take place later this year – provided that Santiago continues his run of good luck in Tokyo with this challenge.

Jake Donovan is an award-winning journalist who served as a senior writer for BoxingScene from 2007-2024, and news editor for the final nine years of his first tour. He was also the lead writer for The Ring before his decision to return home. Follow Jake on X and Instagram.