Yokohama - Japan are a quality side that will be very tough to beat at the Rugby World Cup, Scotland coach Gregor Townsend said on Sunday after his side crashed out with a 28-21 defeat by the Brave Blossoms.

The result saw Japan defy 50/1 odds to go unbeaten in Pool A and set up a mouth-watering quarter-final against South Africa in Tokyo next weekend.

Scotland, however, face an early flight home after missing out to Six Nations rivals Ireland for the pool's runners-up spot.

"We're disappointed, we obviously look at the game from how we play and we weren't able to win by more than eight points," said Townsend.

"We started well in attack and defence but didn't see ball for the rest of half."

Finn Russell opened the scoring with a try, but the hosts, roared on by a capacity crowd at International Stadium Yokohama, hit back with three first-half tries before withstanding a Scottish fightback in the second period.

"At 58 minutes we were seven points behind, but we didn't do enough to get the win," lamented Townsend.

"We came here with high aspirations and getting out of the pool was stage one of that.

"We've worked hard to go further than tonight."

Townsend insisted that the on-off build-up to the match, in light of the deadly Typhoon Hagibis that swept through eastern Japan overnight, had not been behind Scotland's failure to reach the quarter-finals for only the second time in their history.

"It was going to be a challenge with the team we were playing, our (four-day) turnaround," the Scotland coach said.

"The players are professional. We always believed that the game would go ahead."

Townsend added: "It's always a good indication of where the players are with energy when they start and they started well, and then we made a couple of errors, and we gave Japan the ball and they made the most of that.

"I'm proud of the effort, but we need to be more accurate in the final 20 minutes. We had an opportunity to win tonight and we didn't take it."

Townsend praise the Japan team as a "very cohesive group".

"You can tell they've been together for a long time and they know the game they play, they play to their strengths... a fast game.

"They have some really good players, ball-carriers in the forwards and some players (in the backs) with real pace and confidence right now."

Japan play South Africa next weekend and Townsend predicted a tough battle for the two-time champion Springboks.

"They'll be a tough team to beat, that'll be a tough game for South Africa," he said.

Scotland skipper Greg Laidlaw insisted that Japan had "never caught us off-guard as such".

"We started the game fairly well, switched off and let Japan into the game.

"We're disappointed as a group because we had aspirations. They scored 28 points against us tonight and we've got to take that on the chin."