Masamichi Yabuki authored one of the biggest upsets of the year.

The WBC junior flyweight title changed hands for the first time in more than four years, as Yabuki dethroned Kenshiro Teraji via tenth-round stoppage Wednesday evening at Kyoto City Gymnasium in Kyoto, Japan. Teraji saw a late rally nullified as he was trapped along the ropes before the fight was stopped at 2:59 of round ten.

Yabuki insisted from the moment he was assigned to challenge for the title that he was ready to shock the world. The first-time title challenger had to wait twelve days to make good on that promise, as Teraji was forced to postpone their originally scheduled September 10 clash after testing positive for Covid in late August. 

Both boxers were given a clean bill of health ahead of their rescheduled title fight which saw Yabuki rise to the occasion. The 29-year-old challenger from Nagoya jumped out to an early start, putting his one-inch height and two-inch reach advantage to good use. Teraji struggled to work his way inside as he was thoroughly outboxed in the early rounds. 

The first true sign of an upset came when scores were revealed through four rounds (WBC open scoring remains in use in Japan). Yabuki led 40-36 on two cards, while one judge had it even at 38-38. It only served as motivation to continue pushing the action, with Teraji attempting to disrupt the challenger's rhythm but to no avail. 

Teraji punched his way back into the fight in round in the second half. The defending titlist went on the attack in round seven, with Yabuki unable to handle Teraji's aggression for the first time in the fight. 

The trend continued in round eight. Teraji landed enough jabs and left hands to cause redden Yabuki's right eye. Yabuki responded, only to find himself outgunned during several exchanges.

Teraji trailed on all three scorecards after eight rounds, while facing a different kind of adversity as a massive cut opened over his right eye. It only fueled the unbeaten champion to intensify his attack, while fatigue appeared to set in for Yabuki who was now fighting through two badly bruised eyes.

What threatened to serve as a tide-turning moment instead revealed the will of a determined challenger. Teraji had knockout on his mind, of the belief that Yabuki was running on fumes as he sought to close the show. 

Yabuki had one more rally left in him, coming at the perfect time. Teraji once again found himself at the end of Yabuki's long jab and right hand, badly rocked late in round ten and pinned against the ropes. Yabuki continued to let his hands ago until referee Yuji Fukuchi was left with no choice but to halt the contest. 

The late surge by Teraji merely narrowed the gap on the scorecards, as Yabuki led 88-83, 87-84 and 86-85 at the time of the stoppage. 

Yabuki improves to 13-3 (12KOs) with the win, his sixth straight. The feat came on the heels of his lone victory to go to the scorecards, as he claimed a ten-round decision over Toshimasa Ouchi last December. 

The title fight on Wednesday saw Yabuki extended into the tenth round for just the second time, though never more rewarding than the result he was able to produce here. 

Teraji falls to 18-1 (10KOs) with the stunning defeat, which also massively shakes up the junior flyweight title picture. Teraji held the WBC belt since May 2017 following a twelve-round win over Ganigan Lopez, having battered the Mexican en route to an early stoppage win in their rematch one year later. 

The repeat win over Lopez was one of eight successful defenses registered by Teraji, who drew accolades as the best junior flyweight in the world. The division's only other fighter with a firm claim to the contrary was countryman and reigning WBA "Super" champion Hiroto Kyoguchi.

A title unification bout between the two was long discussed though never realistically coming to fruition.

Teraji was on course, however to face IBF junior flyweight titlist Felix Alvarado in a December 2019 tile unification clash. Alvarado fell ill, however, in having to withdraw from their anticipated fight in Yokohama. Teraji wound up facing the man Alvarado beat for the title, Randy Petalcorin whom Teraji dropped four times in a one-sided fourth round stoppage. 

The win was the last for more than a year, with Teraji's career slowed by the pandemic as well as disciplinary action. Teraji was forced to delay a planned title defense versus Tetsuya Hisad last December after crashing his car during a drunk driving incident that was met with a three-month suspension issued by the Japanese Boxing Commission. 

Teraji-Hisada was rescheduled for this past April, Teraji claiming a twelve-round, unanimous decision win for his eighth—and what turned out to be final—successful title defense. 

Yabuki is now poised to pick up where Teraji left off, after throwing his countryman—and the sport—for a loop. 

Yabuki-Teraji aired live on Cantera Doga Pay-Per-View.

Jake Donovan is a senior writer for Twitter: @JakeNDaBox