FUKUROI, SHIZUOKA PREF. –

Japan regular captain Michael Leitch hailed his team's momentous Rugby World Cup win over Ireland on Saturday as a "massive step" toward a first-ever place in the quarterfinals, but warned that nothing has been decided yet.

"We still have a job to do," said Leitch, after Japan had beaten heavyweight contender Ireland 19-12 at Shizuoka Stadium Ecopa, to make it two wins out of two in the tournament so far.

"We talked about it in the locker room that the party finishes in the locker room. We've got to look forward to our next game against Samoa. This (coming) week's game is going to be crucial for us to move through to the quarterfinals."

Japan pulled off another seismic shock at the Rugby World Cup, recovering from two first-half Irish tries to go into the interval only three points behind, and then overtaking Ireland with a superlative second-half performance.

The result immediately went down in legend alongside Japan's 34-32 win over South Africa at the previous tournament in England, but second-row forward Luke Thompson was quick to remind reporters that the Brave Blossoms exited in the first round four years ago despite picking up three wins out of four.

"We've got to go on and make the top eight," said Thompson, who is appearing in his fourth Rugby World Cup and is the oldest player in the tournament at 38. "We're not there yet. We know that in 2015, we won three games and still missed out. It hangs in the background but we're a new team. We know the challenges we have.

"We've still got two really good teams to play against and tonight shows you that if you're not 100 percent on your game, you can lose. So we have to go back out in seven days' time and put in an excellent performance against Samoa. That's all we're focusing on."

Japan plays Samoa on Oct. 5 in Toyota, Aichi Prefecture, before facing Scotland in its final pool match in Yokohama on Oct. 13.

Most observers had expected Japan's game against Scotland to be a battle for second place in the pool, but the Brave Blossoms now have the chance to finish top after a famous afternoon in Shizuoka.

Tries from Garry Ringrose and Rob Kearney gave Ireland an early lead, only for Yu Tamura to kick three first-half penalties to keep Japan within touching distance. A 59th-minute Kenki Fukuoka try then put Japan in front before Tamura widened the lead with another penalty, and a fierce rearguard effort kept the Irish off the scoreboard for the entire second half.

"Out on the field, there was wave after wave coming at us, especially in the second half," said loose forward Pieter Labuschagne, who captained Japan with Leitch dropped to the bench. "It took a special effort from everyone, getting back in line, getting back up. Everyone knew exactly what we wanted to do and we just had to go out there and do it. I'm just really proud of everyone."

Fukuoka missed Japan's opening 30-10 win over Russia after straining his calf muscle in a World Cup warmup game against South Africa on Sept. 6, but the flying winger came off the bench in the 50th minute against Ireland to replace Ryohei Yamanaka.

Fukuoka finished off a piece of quick passing from center Timothy Lafaele to dive over in the corner, and the 27-year-old was happy to play his part despite being denied a second score late in the game.

"Of course, I was feeling a little nervous, but I really wanted to put in a good performance and I had prepared myself for that," said Fukuoka, who ran half the length of the pitch in the 78th minute only to be caught up and tackled by an Irish defender. "I knew as soon as Tim received the ball that he was definitely going to pass it on to me. Tim knew I was there. It's great to get my first try and to score one that really helped the team."

A crowd of 47,813 watched the match at Shizuoka Stadium Ecopa, with the noise reaching almost deafening levels when Japan began to gain the upper hand in the second half.

Leitch came off the bench in the 31st minute to replace the injured Amanaki Mafi, and the regular captain felt privileged to be able to take part in the occasion.

"It was awesome," said Leitch. "It was the best atmosphere I've ever played in. Everyone that has come to Japan for the World Cup is having a great time, and the Tier 2 teams are putting in good performances. I think it's going to be one of the best World Cups ever.

"Four years ago was very special. We went there as underdogs but this time the belief was set from the outset to go out and beat the No. 2 team in the world. That was a hell of a performance and it's great for Japanese rugby."

Ireland will now try to pick up the pieces in its next game against Russia in Kobe on Thursday, with Joe Schmidt's side now fighting for its life despite beginning the tournament with an impressive 27-3 win over Scotland.

"Japan had us under huge pressure today," said Ireland standoff Joey Carbery. "They stretched us and got really good width and depth, and I suppose we're going to have to regroup and take the learnings from it. Hopefully it will make us better."