By James Agberebi:
Goals from Santos' Gabigol (Gabriel) and Paris Saint-Germaine's Marquinhos, sealed the win for the Brazilians captained by Barcelona star, Neymar.
The game was Japan's second friendly since arriving Brazil for the Games.
On Wednesday, they played a 1-1 draw against a local club, CS Sergipe.
Japan will kick-off their campaign at the games against the U-23 Eagles next week Thursday, while Brazil will take on South Africa in Group A same day.