Corinthians midfielder Paulinho beat Japan’s keeper Eiji Kawashima 12 minutes into the game with a low shot from 20 metres.
Santos striker Neymar then put Brazil two goals ahead in the 26th minute, blasting home a penalty awarded after Yasuyuki Konno took down Real Madrid star Kaka.
He added another just after the break with a weak shot deflected into the net by the Japanese defence.
Kaka made it 4-0 in the 76th minute, unleashing a left-foot shot.
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