The win – their first over Samoa on home soil in 15 years – also lifted the Brave Blossoms up one place in the IRB World Rankings to 12th – their joint highest position since the rankings began. Tonga drop to 13th.
Japan and Samoa are scheduled to play each other at RWC 2015 in Milton Keynes on 3 October, 2015.
Argentina also profited from the shock result, taking eighth place from Samoa who now occupy ninth on 75.49 points.
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Lower down the rankings, China move up one place to 67th after clinching the Asian 5 Nations Division 3 East championship – their first Fifteens title of any form for four years – with a 41-10 victory over Guam in Saturday’s final.
Guam slip two places to 90th but they are still above Bosnia and Herzegovina who missed out on a chance to win the European Nations Cup Division 2D title after losing to bottom-of-the-table Finland.
The 29-25 defeat sees Bosnia and Herzegovina drop five places to 91st with Luxembourg moving up to 86th, Swaziland 87th, Tahiti 88th and Monaco 89th. Finland climb two places to 100th, relegating Greece to 102nd and last place.
