Iran survived a scare against Japan to emerge eventual winners and remain on top of Group B with 20 points from four outings. Japan, on the other hand, are second with 10 points from three games.
On Saturday, Iran began brightly and led 6-1 after six minutes as Japan struggled to get a foothold in the game.
Considered as one of the title favourites, Iran looked in brilliant form as they barely gave Japan an inch in the game. Kazuohiro Takano scored Japan's second point as they trailed 2-12 in the ninth minute.
Meraj Sheykh then added four points to help Iran dominate the first half and go 19-9 up at the break.
Iran began the second half in the same dominating style as Sheykh's raid culminated into an all out with Iran leading 26-9 after 23 minutes.
Japan put up a strong fight in the second half and matched Iran for the last 20 minutes before Iran forced another all out in the 33rd minute to lead 35-18.
Japan mounted a strong comeback in the last seven minutes as they scored 10 points in a row to trail 28-35 in the 37th minute. Masayuki Shimokawa scored eight points for Japan in a valiantly attempt to take his team over the line.
In the end, Iran used their experience and held their nerves to fight back against Japan's late show before wrapping up the tie in their favour.