Shooting 55% for the game as a team, the Australians led 25-8 at quarter-time before extending the margin to 26 points at the main break with a 17-8 second term.
The Japanese showed some fight in the second half but the damage had been done as the Opals secured their second victory in as many days.
"We'll continue to do what we need to do," said Australian coach Brendan Joyce.
"We'll keep rotating players, playing smart defensively but we also want to continue to run as we are a quick team.
"Against Japan, we have an advantage inside that we want to use but we are still looking to attack from the perimeter too."
That interior attack saw the Opals record a 57-34 rebound advantage as they were paced by Liz Cambage's 20 points and 12 rebounds. The centre shot 6-9 from the field and 7-9 from the free-throw line while pulling down four offensive boards.
Katie-Rae Ebzery (15 points), Cayla George (13 points) and Steph Talbot (10 points) all reached double-figures while every player hit the scoreboard aside from Sara Blicavs and Tess Madgen who both were absent due to injury once again.
Australia will face Japan in the final game of the warm-up series tonight from 8.30pm AEST