The Japan's men's volleyball team made a losing start under new coach Gary Sato when it was upset in four sets by South Korea in Pool C of the FIVB World League intercontinental round on Saturday.

Many expected that the matchup between the Asian rivals would be tight, but the South Koreans recorded a strong finish, winning 25-22, 25-20, 21-25, 25-19 in front of home fans at Hwasung Indoor Gym.

Despite the disappointment of the defeat, Sato, the first foreign coach of a Japan national volleyball team, said he was proud of his players' efforts.

"We made lots of good plays and today's match was so aggressive," Sato said.

"I'm proud of way that we competed with Korea today. Our team is growing and I'm looking forward to the rest of the matches."

Japan plays South Korea again on Sunday.

The 24th edition of the world's premier annual men's volleyball tournament is being held from May 31 to July 14, with the finals set to take place in Mar del Plata, Argentina from July 17 to 21.

Eighteen teams are divided into three pools of six in the first round. Six teams will qualify for the World League finals featuring the top two teams from Pools A and B, plus the winners of Pool C and the host country.