Japan cruised to a 42-12 victory over battling Chile in Pool D on Sunday after the South Americans marked their World Cup debut with the opening try.

Japan embraced the role of giants in the Toulouse heat, using their pack to bludgeon Chile and score six tries, including five by forwards, after fly-half Rodrigo Fernandez had given the debutants a shock sixth-minute lead.

Four years ago in Tokyo Kotaro Matsushima was the hat-trick hero as the hosts began their tournament with a 30-10 win over minnows Russia.

This time, Matsushima hardly touched the ball as Japan's forwards took the glory, but only after Chile had dared to dream of a historic upset.

The South Americans showed an early willingness to attack from anywhere to the delight of the large crowd and were rewarded at the start of each half.

It took six minutes for Chile to touch down for the first time at the World Cup, but they had to endure an agonising video wait after almost blowing a four-on-one break.

Fullback Inaki Ayarza sliced through Japan's wide defence at halfway before scrum-half Marcelo Torrealba tried to go alone but was stripped in the tackle with players either side of him screaming for a pass.

But Fernandez, scorer of the 2022 world try of the year to get Chile to the World Cup, was following up and dribbled the ball past the defence to touch down.

Chile had a nervous wait before the video match officials confirmed that Torrealba had not knocked on and the try stood, with Santiago Videla converting.

Chile's threat cooled as the temperature in Toulouse climbed to 32 Celsius and Japan's forwards took control on the sun-soaked pitch. (AFP)