Japan's quick play was more than Paraguay could handle as the South Americans were beaten at Kashima Antlers stadium in the Japanese city of Kashima, reports Efe news.
It was the first encounter in Paraguay's Asian tour that is set to include a game against Jordan in Amman, the capital of the Arabic nation, on September 10.
Although Paraguay's Argentine coach Eduardo Berizzo vowed to dominate the possession, the players did not live up to expectations, and the Latin American team seemed unorganized on the pitch, being unable to keep up with the Japan squad's pace.
Japan called up its best team for the friendly with most of the team's players competing in European leagues.
Japan scored both goals within a seven-minute stretch during the first half, as the hosts dominated play against a Paraguayan team that was slow in its reaction. Its midfield was its weakest line.
Werder Bremen's Yuya Osako opened the scoring with an effort in minute 23, while Red Bull Salzburg's Takumi Minamino doubled his country's lead at the half-hour mark.
After the second goal, the Latin American side tried to regain form and get on the scoreboard, but Japanese goalkeeper Shuichi Gonda managed to make two successive saves, clearing striker Braian Samudio's try and the following corner kick.
( With inputs from IANS )