Tonga registered their first win at Rugby World Cup 2011 after seeing off Japan 31-18 in Whangerai on Wednesday.
Having lost to New Zealand and Canada, crowd favourites Tonga finally gave their fans something to cheer about following a well-earned win over an error-strewn Japanese outfit.
The Brave Blossoms had targeted this Pool A match as one of two games they wanted to win, but they were their own worst enemies with ball in hand.
Besides countless dropped passes, John Kirwan's team were turned over (Tonga had nine turnovers to Japan's zero) or penalised far too many times for indiscipline while fly-half James Arlidge failed to land any of his shots at goal.
However, Japan only trailed the Pacific islanders 18-13 at half-time and an entertaining display could have gone either way until midway through the second half when Tonga were able to open up daylight on the scoreboard.
Viliami Ma'afu, Tukulua Lokotui and Fetu'u Vainikolo all crossed for tries, with Kurt Morath slotting over 16 points for the Tongans.
Tonga started the match with a roar and a hiss, threatening Japan's tryline early on only for some terrific defending from the Brave Blossoms keeping them at bay.
Fumiaki Tanaka held number eight Ma'afu up over the line after three minutes but there was no stopping him three minutes later as he powered over from a 5m scrum. Morath missed the conversion.
Japan tied the scores a few minutes later when prop Kensuke Hatakeyama managed to get the ball over the chalk after sustained pressure on Tonga's line.
But Tonga stole the lead again with the easiest of tries from the restart when lock Lokotui made his way over after Japan coughed up possession. This time Morath converted.
Once again, Japan replied with a try of their own when New Zealand-born flank and the game's man-of-the-match Michael Leitch showed incredible strength to power over in the corner.
With Japan down to fourteen men after Arlidge was perhaps unfairly sin-binned by referee Dave Pearson, Morath nailed two penalties to give his team an 18-10 lead.
However it was Japan that finished the half with a flourish as stand-in kicker Shaun Webb slotted over a 39th-minute penalty.
There was little to choose between the two rivals at the start of the second half, but first blood went to Tonga through the boot of Morath.
And the South Sea islanders moved clear when wing Vainikolo made the most of some poor tackling to dive over in the corner for Tonga's third try of the evening.
Tonga, though, were punished for a run of penalties when replacement Halani Aulika was sin-binned - and Japan took advantage of the extra man as centre Alisi Tupuailai crashed over.
Tonga gave themselves a 13-point cushion, though, courtesy of another Morath penalty. And despite Japan's best efforts in attack in the final minutes of the match, they could not find a way through.
Tonga, currently ranked 15th on the IRB rankings, have won five of their 12 games against Japan but they last beat the Brave Blossoms way back in 2006.
Japan's final game is against Canada in Napier next Tuesday while Tonga play France in Wellington on October 1.
Tries: Ma'afu, Lokotui, Vainikolo
Cons: Morath 2
Pens: Morath 4
Tries: Hatakeyama, Leitch, Tupuailai
Tonga: 15 Vungakoto Lilo, 14 Fetu'u Vainikolo, 13 Siale Piutau, 12 Alipate Fatafehi, 11 Sukanaivalu Hufanga, 10 Kurt Morath, 9 Taniela Moa, 8 Viliami Ma'afu, 7 Sione Vaiomo'unga, 6 Sione Kalamafoni, 5 Paino Hehea, 4 Tukulua Lokotui, 3 Taufa'ao Filise, 2 Aleki Lutui (c), 1 Soane Tonga'uiha.
Replacements: 16 Aloisio Ma'asi, 17 Alisona Taumalolo, 18 Halani Aulika, 19 Joseph Tu'ineau, 20 Samiu Vahafolau, 21 Samisoni Fisilau, 22 Viliame Iongi.
Japan: 15 Shaun Webb, 14 Kosuke Endo, 13 Alisi Tupuailai, 12 Ryan Nicholas, 11 Hirotoki Onozawa, 10 James Arlidge, 9 Fumiaki Tanaka, 8 Takashi Kikutani (c), 7 Michael Leitch, 6 Itaru Taniguchi, 5 Toshizumi Kitagawa, 4 Luke Thompson, 3 Kensuke Hatakeyama, 2 Shota Horie, 1 Hisateru Hirashima.
Replacements: 16 Yusuke Aoki, 17 Nozomu Fujita, 18 Hitoshi Ono, 19 Sione Talikavili Vatuvei, 20 Atsushi Hiwasa, 21 Takehisa Usuzuki, 22 Murray Williams.
Referee: Dave Pearson (England)