Following a lengthy reign across two title tenures at 108 pounds, Kenshiro Teraji could no longer make the weight at age 32 and moved up to flyweight Sunday in the co-feature to Takuma Inoue vs. Seiya Tsutsumi at Ariake Arena in Tokyo, Japan. “The Amazing Boy” was visibly undersized against veteran Cristofer Rosales in their meeting for the vacant WBC 112-pound belt, but he had every other possible advantage, and used his tremendous footwork, hand speed, sharp jab, and straighter punches to bloody Rosales’ nose and prevail by stoppage after 10 lopsided rounds.

Rosales, trained by Eddy Reynoso and joined on his ringwalk by stablemate Saul “Canelo” Alvarez, possessed a measured 6½-inch reach advantage, but wasn’t able to do much with it. Thanks to the use of open scoring, he knew he was well behind through eight rounds and offered no objection when the ringside doctor advised referee Laurence Cole to stop the fight after the bell rang to begin round 11 (making this officially an 11th-round TKO).

The bout’s most memorable moment came in round 3, when, after freezing the Nicaraguan Rosales, 30, with jabs and feints alike, Teraji suddenly rocked him with a counter right hand. Rosales wobbled into the ropes, but displayed his experience, holding Teraji and making it through the round.

Rosales experimented with fighting out of a southpaw stance beginning in the fourth, and it paid momentary dividends late in that round, when he landed a single southpaw left hand that nearly put the favored Japanese fighter down.

Thanks to open scoring, the fighters knew after that round that Teraji was up 40-36 twice and 39-37, and the trailing Rosales had perhaps his best round in the fifth — though he also began to struggle with a bloody nose from Teraji’s persistent jabbing.

After the eighth, the scores were 79-73 twice and 78-74, and the only remaining drama was whether The Amazing Boy would force a stoppage or win over the distance. Following a 10th round in which blood continued to spill from the nose of Rosales, 37-7 (22 KOs), Cole officially made it the former.

“I was very, very nervous from the beginning,” Teraji, 24-1 (15 KOs), said after claiming the vacant strap in his new division. He said because of his nerves he could hardly remember what happened across the 30 minutes of in-ring action, and declared, “I’m just happy to be victorious.”