Japan Football Association (JFA) President Motoaki Inukai said the Blue Samurai needed toughening up before the finals in South Africa, which begin on June 11.
"It's the first time in a long time Japan will play South Korea with both teams fielding their best line-ups," Inukai told Reuters before Japan's World Cup send-off at Saitama.
"It is risky, but if you don't take those risks with less than a month to go they don't (get) that sense of what the World Cup is all about."
Japan coach Takeshi Okada has chosen three tough opponents in the run-in to the tournament with fixtures against England and Ivory Coast after their South Korean test.
South Korea have notched 33 wins to Japan's 10 in their previous 61 meetings and their last victory at the East Asian championship earlier this year almost cost Okada his job.
Inukai refused to shake Okada's hand after Japan's team was overpowered 3-1 in Tokyo but insisted he was squarely behind the coach.
