Iran, who had defeated Guam in its opening match in Group B, will play Syria on Sunday.
Mohammad Amini powered the win with 24 points, 8 rebounds, 3 steals and 2 blocks, wreaking havoc at both ends in the decisive fourth quarter.
Sina Vahedi provided the perimeter spark, drilling four triples on his way to 22 points, including the go-ahead basket that triggered Iran’s closing run.
Joshua Hawkinson posted a massive double-double of 20 points and 17 rebounds, while Keisei Tominaga lit up the scoreboard with 22 points and five triples (all in the first half) before fouling out late.
The win moves Iran to 2-0, firmly in the mix to top Group B, while Japan drops to 1-1 ahead of its next assignment against Guam.