This time around, he settled for a landslide lead as he was ahead 40-36 (twice) and 39-37 through four rounds. The bout was sanctioned by the World Boxing Council (WBC), which utilizes open scoring everywhere except for most parts of the United States. 

Guevara didn't let the early lead resonate, enjoying a huge round five as Kimura - who turned 32 this past Monday - looked every bit the overmatched challenger that appeared to be the case on paper. That changed in a big way in round six, when the local underdog turned around the fight and never looked back. 

Body shots proved to take its toll on the defending champ, whose workrate dramatically decreased as the action entered the later rounds. Kimura, meanwhile, found a second wind - or perhaps just finally hit his stride after struggling early. Guevara was still ahead on two cards - 77-75 and 79-73 - while even on a third (76-76) through eight rounds but fading quickly and showing no hopes of turning things around. 

Kimura picked up the pace down the stretch, scoring repeatedly with right hands and left hooks upstairs after his early body attack kept Guevara withing punching range. The defending champ went for one last rally in the 12th and final round, but wasn't enough to extend his title reign as the damage was already done.

Barry Lindenman had the bout 117-111 for Guevara - a rare off-night from the otherwise credible judge from North Carolina who also accurately scored Saturday's main event in favor of Carlos Cuadras over Koki Eto. The upset was not to be denied, however, as judges Jun Bae Lim and Noppharat Sricharoen turned in identical scores of 115-113 in favor of Kimura. 

The win is by far a career-best moment for Kimura who improves to 18-2-1 (3KOs). The closest he'd previously come to title fight experience was a knockout loss to Ryoichi Taguchi when both were still prospects in Oct. '11. It was the last time he'd seen the loss column, having won nine straight including Saturday's stunner.

Guevara falls to 26-2-1 (17KOs), having previously won eight straight. His title reign comes to an end after just 11 months, beginning and ending in Japan. The defending champ from Mazatlan, Mexico - where both of his two successful title defenses were staged earlier this year - was as much as a 13-1 favorite heading into fight night, certainly qualifying as one of the biggest upsets of 2015.   

Jake Donovan is the managing editor of BoxingScene.com. Twitter: @JakeNDaBox