Ohtani, the MVP from three years ago, and Suzuki combined in the early going with home runs in a topsy-turvy encounter.
Tied heading into the seventh, Japan would score three runs to see themselves to a 2-0 record in Pool C play.
After their dominant win over Chinese Taipei, Japan's fans in Tokyo would have been looking for more of the same against South Korea, but they were silenced early as the opposition put up a three-spot in the first inning.
Starting Yusei Kikuchi gave away two singles to start the contest before Moon Bo-Gyeong, who hit a grand slam earlier in the WBC, doubled to drive in a pair after Lee Jung-Hoo had opened the scoring with a single.
It didn't take long for Japan to respond. After an Ohtani walk, Suzuki got hold of a slider from Ko Young-Pyo to send it over the fence into the opposite field.
It would be that pair of Japanese hitters who would put their side ahead in the third. Ohtani clobbered his second home run of the tournament, before Suzuki did the same in the next at-bat. Masataka Yoshida then immediately joined the hitting party, cracking a solo shot of his own to make it 5-3 to the home side going into the fourth inning.
This was billed as the best match of Pool C, and it was living up to the hype. South Korea answered back quickly. Hyesong Kim was the man to draw the scores level again, with a stunning two-run blast.
The bullpens then came into their own to keep it quiet as the game reached the seventh, but Korea would blink first as an erratic Park Yeong-Hun walked in a run before Yoshida sent a single up the middle to drive in a pair of runs.
Now 8-5, Japan seemed to have turned the tide, but Korea kept it close with Kim Jo-Wun pumping a single through the infield to make it a two-run game heading down the stretch.
Japan held on for the win with Taisei Ota getting the three outs needed, and he was helped out by Ukyo Shuto, who produced a stunning catch in centre field up against the wall.
Check out the full scorecard and stats with Flashscore.
Chinese Taipei unleash on the Czech Republic
Earlier in the day, Chinese Taipei picked up their first win of the WBC, pulverising the Czech Republic 14-0 to mercy the game after seven innings.
Stuart Fairchild set the tone early, hitting a grand slam off of starter Jan Novak, before Yu Chang took centre stage, going 3-for-5 and driving in four runs. Chinese Taipei scored in five of the seven innings, whilst the Czech bats ran cold again, with just four hits in the loss.
The Czech Republic are now 0-3 in the pool, and know they must beat Australia to have a chance of avoiding bottom spot in the group, which would force them to have to qualify for the next edition of the Classic.
Chinese Taipei face South Korea on Sunday morning at 04:00 CET, knowing they must win to have any chance of qualifying for the knockouts.
The WBC continues later this afternoon as Canada and Italy all make their bow in the tournament.
