Japan stayed on course for its seventh straight Asian 5 Nations title and more importantly its eighth successive appearance at a Rugby World Cup following a 132-10 thrashing of Sri Lanka on Saturday.

The Brave Blossoms ran in 20 tries at Mizuho Rugby Ground in a game that did nothing but highlight why the elite division in Asian rugby is being cut to three teams from next year.

As Suntory Sungoliath coach Andy Friend tweeted after the slaughter of the Elephants had been brought to a halt by the final whistle, "Need to question the worth."

The only good thing that came out of the game — which saw Japan record its third-highest score and third-biggest winning margin in test match rugby — was that the Brave Blossoms gave a reminder to South Korea and Hong Kong that they are in no mood to relinquish their crown as the No. 1 team in Asia.

"We aim to be the greatest-ever Japan team so we should be breaking records," head coach Eddie Jones said after the game. "I am obviously pleased with the result as we have played two games and have maximum points. We are exactly where we want to be and all our thoughts now are on beating Korea next week."

Sri Lanka captain Namal Rajapaksa, whose side lost 59-3 to the Koreans and 41-10 to Hong Kong before traveling to Japan, was in no doubt as to who will win the A5N and qualify automatically for the World Cup.

"South Korea should be able to give Japan a good fight, but Japan are much more professional and much faster and more skillful," he said.

Rajapaksa spoke before Saturday's other game finished, as he may have adjusted his answer slightly.

Hong Kong beat South Korea 39-6 to make it three wins from three games and set up what should be a winner-takes-all clash with Japan at National Stadium on May 25.

Jones, however, was not looking that far ahead.

"Korea away and at home are two different beasts and we need to recognize that," he said. "Next week they will have home support and the referee will be influenced. We need to smash them in the first 20 minutes and put the game in no doubt."

And that's exactly what Japan did in Nagoya.

The game was just three minutes old when Yasuki Hayashi crossed for the first of Japan's tries, and the Brave Blossoms went on to average a touch down every four minutes.

Ayumu Goromaru scored one try and added 16 conversions — a new Japan record — to finish the day with 37 points, hooker Takeshi Kizu scored a hat-trick in the opening 25 minutes and captain Michael Leitch also bagged three tries.

There were also braces for Akihito Yamada, Hendrik Tui and Ryu Koliniasi Holani as Japan made the most of its huge weight advantage up front.

"We wanted to play it tight for the first 30 minutes and we did that," said Leitch. "We then wanted to play it close to 10 and we did that, and we put a lot of pressure on them in the scrum and maul."

To their credit, the Sri Lankans never gave up and Fazil Marijah's try in the 69th minute was rewarded with the biggest cheer of the night. But as Jones pointed out using a cricketing analogy that the visitors would have understood but was lost on the local media, "I told a mate that if we won the toss we would bat first. We did and got a big score and would have declared after 20 minutes."

The remaining 60 minutes was nothing more than a training run.