Eduardo Nunez boxed brilliantly from start-to-finish and proved too much for a defiant Masanori Rikiishi display, en route to capturing the vacant IBF world junior lightweight title with a 12-round unanimous decision victory on away turf.

115-113, 116-112, 117-111 read the scores after an exhausting encounter in Yokohama, Japan during the co-main event of a world championship doubleheader led by Ohashi Promotions. The main event saw Yoshiki Takei retain his WBO bantamweight title with a 1st-round TKO win over Yuttapong Tongdee.

Nunez (28-1, 27 KOs) didn't have it all his own way but was a clear victor over Rikiishi (16-2, 11 KOs), in the home favourite's toughest test yet. Yet, he deserved to hear the final bell.

Nunez, with promoter Eddie Hearn proudly standing in his corner, had opportunities to showcase his vaunted punching power on another away trip after stoppage victories over former champion Shavkat Rakhimov and longtime contender Miguel Marriaga in 2024.

Nunez stalked his prey from the opening bell, staying low and pressing forward to negate the noticeable size difference between them. He whipped right hands furiously and while partially blocked, they were scoring shots for the Mexican as Rikiishi replied downstairs.

The 27-year-old's protruding back muscles served as a visual warning of where the power comes from, Rikiishi stumbling backwards early in the second stanza after being peppered with lefts to the body. The home hopeful sought to spin off away from danger with defensive counterpunching and cuffing hooks, missing with a right uppercut before the bell.

Nunez missed wildly during a frustrating third prompted brief celebratory reactions from the crowd as Rikiishi circled the ring with his jab landing and flashing uppercuts, the 30-year-old's confidence steadily improving as time wore on - though danger still lingered.

That was clear in the first minute of the fourth, Nunez moving his head off centre line more and connecting on two-punch combinations to make Rikiishi increasingly uncomfortable as their close-range exchanges were making for compelling viewing.

Left to the body and then an uppercut was Nunez's combination of choice in the fifth and Rikiishi couldn't move away fast enough or counter cleanly with enough regularity to deter the younger man's bruising work. The Yokohama crowd could sense their man needed encouragement and duly obliged, as he landed stiff flurries in a frantic finish to the frame.

Rikiishi's body work was prompting Nunez to fire more shots with the southpaw pressed up against the ropes during a tiring sixth, his sharp intake of breath between sequences saying all it needed to, as they entered the second-half of a matchup with both landing big shots.

Constantly looking to reply whenever Nunez would unload a combination, he couldn't let the Mexican tee off on him as the varied attacks persisted, body-then-head and vice versa, several shots unanswered and then suddenly, Rikiishi would respond gamely again.

Every punch he would land almost seemed to spur Nunez on further, as they ended the seventh with the bigger man finishing strongly at the end of a stanza he was second best in.

The crowd noise swelled at the sight of Nunez stumbling Nunez early in the eighth, no more than just a loss of footing and a punch absorbed while off-balance as Rikiishi still circled the ring, being made to work tirelessly in a concerted effort to nullify the Mexican's better work.

One couldn't help wondering what the in-form Anthony Cacace (24-1, 9 KOs) would've been thinking had he been watching this fiery duel for a title he vacated, while Hearn-backed former featherweight champion Raymond Ford (17-1-1, 8 KOs) had been linked in an in-house promotional matchup.

There was an inevitability to Nunez's work here that you couldn't help but forecast future junior lightweight bouts for an all-action fighter yet to breakthrough into the mainstream.

Nunez's relentless work up close was exhausting and starting to take its toll on Rikiishi, whose back was a cherry red colour and the resistance waning ever so slightly. He wobbled him with a pair of sickening right hands early in the tenth, Rikiishi evading caution after forcefully pushing the Mexican back - but only briefly - as his defences were pierced again.

Rikiishi landed a nice counter left hook in the final seconds, but was being thoroughly outgunned in what looked like a firefight he couldn't escape with two rounds remaining.

Nunez chased more than he probed in round eleven, knowing Rikiishi was exhausted and rigidly sticking to his counterpunching tactics with reduced lateral movement to boot.

An uppercut and sweeping left hand scored well for the home favourite during a busy final frame, knowing he needed something special to finish with a flourish, though he wasn't given a chance for any respite and continued attacking off the back foot. A vicious right hand in the final seconds was the exclamation point on another fantastic away showing.