Second-row Amato Fakatava scored two tries as Japan defeated Chile 42-12 with a bonus-point performance at the Stadium de Toulouse in Pool D on Sunday.
Fly-half Rodrigo Fernandez scored Chile's first ever Rugby World Cup try but Fakatava grabbed his first shortly afterwards before wing Jone Naikabula added a second after Chilean prop Matias Dittus was shown a yellow card.
Chile were again reduced to 14 men after captain Martin Sigren was sin-binned before half-time and Fakatava added another try to give Japan a 21-7 interval lead.
Brave Blossoms centre Dylan Riley also received a yellow card before number eight Alfonso Escobar reduced Chile's deficit with their second try but scores from flanker Michael Leitch, inside-centre Ryoto Nakamura and replacement second-row Warner Dearns embellished Japan's victory margin.
Fakatawa, the Mastercard Player of the Match, said it was a "pretty tough" start to their campaign, with matches to follow against England, Samoa and Argentina.
"We expected Chile to come out strong. It's pretty hot but I was happy to be out there with the boys. My first World Cup...unbelievable. I don't know how I made it here."
Japan captain Yutaka Nagare said it was "really important" his side had prevailed in a vibrant atmosphere in Toulouse.
"It's great to see all the fans supporting us today, it's a great atmosphere," he added. "We struggled a little bit against the Chileans' physicality but we executed our game-plan which was great for us."
Brave Blossoms head coach Jamie Joseph was pleased to come away with a bonus-point victory after Chile closed to within nine points early in the second half.
"Chile came with a really spirited performance, really hearty, tackled like demons, turned our ball over, really put us under pressure," he said. "We had to deal with that without losing confidence."
His Chile counterpart Pablo Lemoine felt a lack of experience cost his side in the final quarter as Japan scored three more tries.
"We were OK for 60 minutes but in the last 20 minutes we missed some experience to manage the game and Japan were amazing with their efficiency," he said.
