Japan rode a 25-point game from emerging star Rui Hachimura to claim a must-win Asian World Cup qualifier over Iran in Tokyo on Monday.

The 70-56 victory at Ota City General Gymnasium, Japan's fourth in a row, keeps its hopes of qualifying for basketball's first World Cup alive, with the win over the undermanned Iranians ensuring it stays in touch with the top teams in its group.

The Gonzaga University big man Hachimura added seven rebounds, three assists and two steals, with Memphis Grizzlies signee Yuta Watanabe's 18 points, 14 in the second half, helping Japan break the game open in the third period.

Without key players and top-two scorers, Mohammadsamad Nik Khahbahrami and Hamed Haddadi, Iran was unable to maintain its torrid early pace, Behnam Yakhchalidehkordi leading with 21 points while Meisam Mirzaeitalarposhti added 10 and eight boards.

"Watanabe and Hachimura make the Japan national team better every time, when they play," said Japan's Argentine head coach Julio Lamas of his two young stars who will soon head back to the United States.

"Every time, when they play, it is good news for us. When they don't play it is bad news for us. They are very complete, in defense and offense...They are athletic, (and) our team has an upgrade in size when they play in the three and four positions."

"It is a very good victory for us, a very good win and we are very happy," he said.

(Rui Hachimura)

Iran opened shooting well, Yakhchalidehkordi knocking down three of his team's four from deep in the first quarter, but Japan played disruptive defense and got to the line to keep the deficit at just six points going into the second period, Hachimura pacing the home team with eight points.

The visitors refused to cool off in the second, stretching the lead to 10 early in the period, but Japan rallied, Watanabe getting a steal at mid-court before making a driving lay-up to even the score at 26, pumping his fist as Iran called a timeout.

Iran proved resilient, however, and after it hit its second buzzer-beater in as many quarters, the Middle Eastern team took a 35-31 lead into halftime.

After shooting 1-for-9 in the first half, Watanabe got going early in the third, Makoto Hiejima and Yuki Togashi finding him some easy buckets in transition.

Japan shot 11-for-16 in the third, and closed with an 8-0 run, going into the final stanza with a 57-43 lead.

Iran was unable to muster a run in the final period, and Japan closed the game out.

"Our team defense was good for 40 minutes, but was much better in the second half," said Lamas. "They scored just 21 points (in the second half)...we played better in offense too with better ball circulation."

(Hachimura, 23, and Yuta Watanabe, 12, celebrate Japan's victory)

The top three teams from each group plus the next best team from either side of the draw qualify for the World Cup in China next year. Japan is challenging the Philippines for third place in Group F, and may still qualify if China and Jordan falter in their race for fourth in Group E.

Japan's next two games against Qatar on Nov. 30 and Kazakhstan on Dec. 3 are must-win, and the Akatsuki Five will have to hope the Philippines stumbles in one of its remaining three games in order to qualify directly from its group.