Japan baseball manager demands more after thrashing arch-rival Koreans

Japan's World Baseball Classic manager warned that his team can still get better after they thrashed arch-rivals South Korea on Friday for their second straight win of the tournament.

Superstar Shohei Ohtani kept the Tokyo crowd waiting for his first home run but his team-mates were clinical in dismantling the Koreans 13-4 to move a step closer to the quarter-finals.

Japan did have to dig themselves out of an early hole before establishing their dominance, and manager Hideki Kuriyama wants to see improvements when they face the Czech Republic on Saturday.

"Baseball is always a difficult game for a manager but my players are always focused on scoring or minimising runs," he said.

"That is what led to this win tonight but we still have things we have to work on for tomorrow."

The game could have been a different story if Korea had capitalised on the three runs they scored in the third inning off starting Japan pitcher Yu Darvish.

Darvish -- the team's biggest star after Ohtani -- gave up three hits including a home run before leaving the game after the third inning.

Darvish said he was happy with the speed but not the control of his pitches, but he was "OK with it considering it was my first start of the year".

"This was my first game in Japan for a long time and it was special for me," said the San Diego Padres veteran, who threw the pitch that clinched the 2009 World Baseball Classic title for Japan.

"I might not have many more chances to play here."

Japan, fuelled by another tenacious performance from American-born Lars Nootbaar, overturned the deficit straight away, scoring four runs in the bottom of the third.

They then opened up a comfortable lead, with Masataka Yoshida of the Boston Red Sox making a big contribution with three hits and five RBIs.

Los Angeles Angels star Ohtani finished with a double and a single and scored two runs.

Japan's Prime Minister Fumio Kishida threw out the ceremonial first pitch before the game, but his looping effort fell some way short and wide of the catcher's glove.

South Korea are now in real danger of elimination after suffering a shock loss to Australia in their opening game.

Elsewhere in Pool B, the Czechs claimed a dramatic 8-5 win over China in their first-ever game at the tournament.

In Pool A, being played in Taiwan, Cuba beat Panama 13-4 for their first win of the tournament and Taiwan beat Italy 11-7.