Nishida was on top form as he guided his team with 21 points, 2 aces and one block on his own.
To edge out a solid Iranian side, Japan relied on a team performance as Masahiro Yanagida (17 points, including 3 aces), Tatsuya Fukuzawa (11 points), Akihiro Yamauchi (12 points) and Haku Ri (15 points) all managed double digits.
Amir Ghafour, who was Iran's top scorer on 18 points against France on Friday, only managed to score six points against Australia. The opposite spike was on top form for this Asian derby, claiming 22 points (including 4 blocks), almost double the total of Seyed Mohammad Mousavi Eraghi (12).
Japan now heads to Goaiana (Brazil) for week 2 while Iran is going to San Juan (Argentina), hoping to do better.
The competition is being held from May 25 to July 8 in 22 host cities.
The 16 teams compete in a round-robin format with every core team hosting a pool at least once. The teams are divided into four pools of four teams at each week and compete five weeks long, with a total of 120 matches.
The top five teams after the preliminary round join the host of the final round to compete in the final round.
The relegation takes in consideration only the 4 challenger teams. The last ranked challenger team plays the promotion play-off against the Challenger Cup winners. The winners of the play-off will qualify for the next edition as a challenger team.