They were a perfect 7-0 through this year's edition.
The contest ended in a duel that is likely to go down in baseball folklore as Ohtani, the hitting and pitching sensation from Japan, faced off against his Los Angeles Angels teammate and U.S. captain Trout.
"Whether I got him out or he got a hit off of me, I didn't want to have any regrets," said Ohtani through an interpreter. "I wanted to make my best pitch.
"This is a different experience, representing your country and facing guys representing their country. It was a different intensity and it was great."
Carrying their nation's flags, the two men had led their respective teams onto the field and then at the climax, in a moment of pure sporting magic, stood across from each other with everything on the line.
With Japan clinging to a 3-2 ninth inning lead they turned to their ace Ohtani.
He walked the first batter he faced in Jeff McNeil but then got Mookie Betts to hit into a double play, bringing up Trout with two out and the sellout crowd on its feet.
Throwing 100 mph fastballs Ohtani struck out his Angels teammate on six pitches to trigger celebrations as the Japan team poured out of the dugout.
OHTANI THE 'UNICORN'
Japan manager Hideki Kuriyama said the win could have a big impact on the sport's popularity back home.
"... all the kids in Japan who are watching that might think, 'Oh, that's really cool', and they might want to make up their mind to want to be baseball players".
U.S. manager Mark DeRosa said it had been a storybook ending for the baseball world but that he had hoped "it would end a little bit different with Mike popping one".
"The whole world got to see Ohtani come in, big spot, battling. It's kind of how it was kind of scripted," he told reporters.
He also heaped praise on Ohtani, saying, "no moment's too big for him".
"What he's doing in the game is what probably 90% of the guys in that clubhouse did in Little League or in youth tournaments, and he's able to pull it off on the biggest stages. He is a unicorn to the sport."
Ohtani was named the WBC's Most Valuable Player after posting the best statistics over the entire tournament.
U.S. shortstop Trea Turner provided the early fireworks with a second inning solo shot, taking Shota Imanaga into the left field bleachers for his fifth home run of the WBC to give the U.S. a 1-0 lead.
Japan answered right back in the bottom of the inning, slugger Munetaka Murakami, who drove in the two runs in Japan's walkoff semi-final win over Mexico, slamming a home run to deep center off Merrill Kelly.
After Kelly loaded the bases DeRosa had seen enough, making the switch to Aaron Loup, who would get them out of the inning but not before Lars Nootbaar grounded out to first to score Kazuma Okamoto with the go-ahead run.
Okamoto added to Japan's lead with a home run to lead off the bottom of the fourth.
And Japan had a huge opportunity to put the contest out of reach in the sixth when Jason Adams walked three to load the bases, but Nootbaar flied out meekly to right to end the threat.
With the U.S. running out of innings Kyle Schwarber, the National League's home run champion, slammed a monster homer off Yu Darvish in the eighth, taking him into the upper deck to trim Japan's lead to 3-2.
Ohtani described Japan's triumph as the best moment of his life and said he has already set his sights on the next edition of the global showcase in 2026..
"This is the best moment in my life," Ohtani told reporters. "Just because we won today doesn't mean that we achieved a final goal, this is just a passing point. Our team has just started, so I think we need to tune-up for the future.
"I think the next (WBC) is three years later, I'm going to have to keep the same level and hopefully I'll be a better player ... I would love to enter again.
"I've seen Japan winning and I just wanted to be part of it. I really appreciate that I was able to have this great experience. The next generation, the kids, I was hoping that those people would like to play baseball. That would make me happy."
Ohtani also delivered a fiery speech to his teammates before the game, telling them not to be overawed by the star-studded U.S. team.
"Just looking at the great lineup of players ... obviously, we have respect, but at the same time, it looks like we might be beaten down," Ohtani added.
"So just forget about those kind of feelings, we're just even, we just have to beat them - I just wanted to bring that feeling up among us.
"This really proves that Japanese baseball can beat any team in the world."