Hiroki Sekine forced Roberto Fernandez into an early save when he steered Yamamoto’s corner goalward while at the other end Marcelo Fernandez shrugged off Kota Takai to fire into the side-netting but, within six minutes, Japan were in front.

Koki Saito’s perfectly weighted pass released Ayumu Ohata down the left and the Urawa Red Diamonds defender’s cut back found Mito with the space to clinically strike into the bottom corner of Fernandez’s goal.

A reckless challenge from Viera, when he caught Hirakawa above the ankle with his studs, resulted in the midfielder seeing red after French referee Francois Letexier consulted the pitch side monitor.

Japan were initially unable to make the most of the numerical advantage with Sekine’s wayward shot from distance and an injury time strike that was kept out by substitute Kein Sato their only opportunities of note before the interval.

Despite being a man down, the Paraguayans picked up the pace at the start of the second half and Fernandez hit the side-netting in a warning to Oiwa’s team.

But by the 63rd minute Japan had doubled their lead, Mito applying the finishing touch to a period of dominance that resulted in Saito clipping the ball over from the touchline for the playmaker to drive his diving header home.

Yamamoto struck from the edge of the area six minutes later to put Japan further ahead and substitute Fujio headed in the Ryotaro Araki’s free kick eight minutes after replacing Mito.

The Machida Zelvia forward then raced onto Hosoya’s through ball to score the fifth as Japan made a strong start to their Olympic campaign.