|Villami Ma'afu stretches over the line for Tonga's first try [GALLO/GETTY]
Tonga beat Japan 31-18 in an open, entertaining and error-ridden clash on Wednesday to keep alive their slim hopes of reaching the Rugby World Cup quarter-finals for the first time.
Tonga's hulking forward pack enjoyed total dominance during scrum time but they failed to make the most of their obvious physical advantage at the Northland Events Centre.
That lack of discipline and poor decision-making kept Asian and Pacific Nations champions Japan in the game.
Tonga must beat France in their final game with a bonus point and hope the Europeans lose to New Zealand heavily on Saturday to have any chance of reaching the last eight.
"We just needed to get a win," Tonga captain Aleki Lutui said in a pitchside interview after avenging their 28-27 defeat by Japan in the Pacific Nations Cup in July.
"We are proud of our performance today but that's not the end of the road, we've got another game next week."
The Tongan forwards tore into the Japanese from the kickoff after Japan captain Takashi Kikutani spilled the ball from a huge hit in his own 22 in the opening play.
Six minutes of Tongan pressure followed before number eight Viliami Ma'afu drove over from short range after the Japan scrum had been wheeled towards the touchline under immense pressure.
The Japanese forwards looked rattled but bounced back from their early roughing up to snatch a try with their first attack in the 14th minute through Kensuke Hatakeyama.
The prop picked and drove over from the back of a ruck on the Tongan line and, despite appearing to make a double movement, was awarded the score by the video referee.
Tonga, however, replied instantly when lock Tukulua Lokotui was on hand to run in an easy overlap after the ball had popped out of the ruck on the Tongan side from the restart.
Flyhalf Kurt Morath converted from near the left touchline but Japan came roaring back in the see-sawing encounter.
Slack Tongan defending allowed Japanese inside centre Ryan Nicholas to break through and, after quick recycled ball and another slick handling move, flanker Michael Leitch was able to power over in the corner for their second try.
The two sides gave away 27 penalties between them and Morath was on form with the boot and slotted another in the 28th minute to extend the lead.
Morath's counterpart James Arlidge was having a far worse evening and, after failing to convert the opening two tries, he was sin-binned in the 31st minute after racing into an offside position to intercept a pass as Tonga threatened once again.
Morath kicked the three points to extend the lead to 18-10 but despite being a man down, fullback Shaun Webb kicked a penalty just before the break for Japan's "Brave Blossoms" to close the gap to five.
Tonga ran in their third try in the 54th minute when winger Fetu'u Vainikolo cut inside and barged through a poor tackle by Arlidge to score.
Morath converted to stretch the score to 28-13 as the Tongans threatened to cut loose.
But more ill discipline cost them as replacement prop Halani Aulika was shown a yellow card with 20 minutes to go after Tonga were deemed guilty of persistent offending by English referee Dave Pearson.
Japan made the most of the numerical advantage and centre Alisi Tupuailai cut back on a sharp line to crash over and close the gap to 10 points but Arlidge was again wayward with the conversion.
Morath's slotted his fourth penalty for a 31-18 lead in the 67th minute and despite late pressure and lock Lokotui being shown a yellow card, Japan could not close the gap to earn a bonus point.
"The game itself was so tough. We apologise for not being able to win," Kikutani said in a pitchside interview.
"We will keep up our good work against Canada, we will never give up."