Shohei Ohtani kept the Tokyo crowd waiting for his first home run of the World Baseball Classic, but in the end Japan thrashed arch-rivals South Korea 13-4 Friday for their second straight win.

Los Angeles Angels superstar Ohtani hit a double, a single and scored two runs as Japan dug themselves out of an early hole to move closer to a place in the quarter-finals with a dominating performance.

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

San Diego Padres star Darvish – Japan's biggest name after Ohtani – gave up three hits including a home run before leaving the game after the third inning.

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

Japan then stretched their legs with more runs before the game was over and now stand on the brink of the last eight, with the Czech Republic next to play on Saturday.

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

Japan have won the World Baseball Classic twice and beat the Koreans in the final of the 2009 tournament.

Darvish closed out that game to clinch the title but he endured a frustrating evening on his return to the tournament after a 14-year absence.

Japan's batters had no such problems, with Masataka Yoshida of the Boston Red Sox finishing with three hits and five RBIs.

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. (AFP)