In a tournament that went down to the wire, the John Kirwan-coached Japan needed to beat Fiji and score four tries for the bonus point if they were to overtake Tonga on a countback at the top of the table.
The odds looked stacked against them when they trailed 8-0 at halftime and had trouble containing the bigger Fijians.
But as the game progressed Irish referee Peter Fitzgibbon punished Fiji for a lack of discipline with three yellow cards and two reds, allowing Japan to take advantage of the numerical imbalance.
They scored three quick tries to hold a 17-13 lead with 15 minutes remaining but the vital fourth try proved elusive until deep in injury time when Fiji were down to 12 men and Imamura carved through the stretched defence.
Go Aruga, Ryan Nicholas and Shota Horie also scored for Japan with Shaun Webb landing two conversions.
Fiji’s points came from two tries by Napolioni Nalaga and a penalty to Seremaia Bai.
An elated Kirwan achnowledged Fiji were the more physical side but said they paid the price for indiscipline.
“It was Fiji’s indiscipline that helped us in the win,” he said.
“The halftime message was to keep possession. In the first half we were not playing to our game plan.
Fiji captain Dominiko Waqaniburotu said it was difficult for his side to keep to their game plan as for nearly half the game they had at least two players off the field.
“Our set piece didn’t work because we kept having players sent to the sin-bin and red-carded.”
The Fijians sent from the field were all penalised for dangerous tackles with Sale Sharks backrower Sisa Koyamaibole given the first red card midway through the first half and centre Seru Rabeni was dismissed in the second half.
Until Imamura’s try, Tonga felt the tournament was theirs after they beat defending champions Samoa 29-19 in their final game.
Having beaten Fiji in the first round, Tonga finished with two wins and two bonus points for 10 points from their three matches and they had the best points differential with the most points scored and the tightest defence.
But the bonus-point try for Japan against Fiji also lifted them to 10 points and the championship was decided by the outcome of the clash between the two top teams last week in which Japan narrowly beat Tonga 28-27. SOURCE: AFP