Hat-trick hero Kotaro Matsushima is backing Japan to shake off its Rugby World Cup stage fright before it plays Ireland next weekend, after the host nation recovered from a nervy start to beat Russia in the tournament opener on Friday night.

Japan got the first Rugby World Cup ever to be held in Asia off to a winning start with a 30-10 victory over rank outsider Russia, but only after freezing in the early stages of a match watched by 45,745 expectant fans at Tokyo Stadium and millions more all over the world.

Russia almost scored in the first minute before a mistake by Japan fullback William Tupou four minutes later gifted Kirill Golosnitskiy the tournament's opening try, and it took two scores from Matsushima to steady the ship and send the Brave Blossoms into halftime with a narrow lead.

Pieter Labuschagne then gave Japan some breathing space with another try at the start of the second half, before Matsushima completed his hat trick with a searing run to also claim a bonus point for the home team.

Matsushima became the first Japanese player ever to score a hat trick at the Rugby World Cup, but the winger was left ruing the chances he missed and vowing to set the record straight against world No. 1-ranked Ireland in Shizuoka on Sept. 28.

"I think I was able to have a look around me and see where the space was today," said the 26-year-old. "But I had some mistakes and knock-ons, and I think I could have scored more. That doesn't just go for me but for the whole team as well. We have tougher games coming up, and we need to be able to finish off the chances when they come.

"Everyone was more nervous than I thought they would be. It was a World Cup atmosphere. Hopefully we'll have worked that out of our system by the time we play again next week."

Japan looked shell-shocked when Russia, which did not even qualify for the tournament and only claimed a place because Romania and Spain were penalized for fielding ineligible players, came charging up the field straight from the kickoff.

Tupou soon made a complete mess of a Russian up-and-under deep in Japanese territory, and the fullback could only watch in horror as Golosnitskiy scooped up the loose ball to run over for the fastest try ever scored in a Rugby World Cup opening game.

"To be honest, because it's my first World Cup I was a little nervous, but with that high ball, I should have caught it," said Tupou. "I'm not going to make any excuses. I've just got to be better next time."

Japan recovered to take control of the match and also secure a bonus point for scoring at least four tries. Failure to win bonus points was what cost Japan a place in the quarterfinals at the 2015 Rugby World Cup in England despite winning three games out of four, and try-scorer Labuschagne was relieved to claim one at the first time of asking in this year's tournament.

"We managed to get four tries over the line and get the bonus point," said Labuschagne, who stripped the ball clean away from a Russian player before galloping over the line for his 47th-minute try. "We're really delighted about the win but really happy about the bonus point as well.

“The opportunity was there for my try and I got the ball, saw the line and just tried to get there as quickly as possible. The guy caught up, but I could hear the support catching up as well so I felt pretty confident. Once I crossed over the try line, I was filled with happiness. It was a great moment.”

Japan head coach Jamie Joseph and his players will now turn their attentions toward Ireland, which opens its campaign against Scotland in Yokohama on Sunday. The Irish have beaten two-time defending champion New Zealand twice in the last three years and have won the Six Nations three times since 2014, but Joseph says his players will not be daunted by the challenge.

“I think the pressure is always going to be on the players because the expectation of themselves is so high,” he said. “We’ve talked a lot about the home World Cup, and home nations generally always have those high expectations. The fact that we’re a Tier-Two team and we’re playing the team ranked the best in the world, it doesn’t change anything really for us. We’ve set our goals, just like the rest of the teams.

"With Ireland, it's going to be a difficult test match. Anyone who plays them will understand that. So internally, the pressure will be on. But externally, I don't think anyone gives us a shot outside of Japan."

Russia is straight back in action against Samoa in Kumagaya, Saitama Prefecture, on Tuesday, and head coach Lyn Jones knows his side is up against it in the tournament.

"The trick for us now is to get recovered, get fresh legs and turn up with a little bit more confidence," said the Welshman. "We appreciate that we had a 20 percent chance to win tonight, and everything needed to go right for us.

"I'm very proud of our players. They stuck in there and gave everything they had for their nation. At the end of the day, it's a very somber changing room. The players are disappointed. They thought they could have had a very close game, but it wasn't to be tonight."