Tanner Chun doubled in the go-ahead run, then scored on a single by Sean Yamaguchi in the top of the seventh inning as unseeded Saint Louis rallied to knock out OIA champion Kailua, 6-4, on Wednesday night at Les Murakami Stadium.

Saint Louis (16-7) advanced to the semifinals of the Wally Yonamine Foundation/HHSAA Baseball State Championships and will meet MIL champion Maui today at 4 p.m.

Kailua had a 4-0 lead after two innings, but Saint Louis never flinched.

“For us, facing Kailua it’s always going to be a battle,” Crusaders shortstop Yamaguchi said. “They’re going to run a lot, put the ball in play, so we had to play good baseball. Throw a lot of strikes.”

The Crusaders rode the pitching of junior La‘akea Correa, who went 31⁄3 innings, and sophomore Aycen Fernandez, who pitched 32⁄3 scoreless, hitless innings and earned the win.

“We couldn’t get anything off him,” Kailua coach Corey Ishigo said. “We did all we could. We prepared as best we could. It just didn’t go our way tonight. Saint Louis is just a good team. All the credit goes to them.”

Fernandez didn’t have his full arsenal, but was in full command of his fastball and change-up.

“I knew I had to throw strikes. I feel good. Exhausted,” he said. “It’s support. I got trust in my defense. Trust in my coach’s pitch calling. Trust in my catcher.”

He struck out three and walked three on 59 pitches, further cementing his place as one of the state’s best closers.

Coach Benny Agbayani said Fernandez simply can’t stop moving.

“He can’t keep still. He wants the ball. He wants to be on the field. His job is to be a pitcher and he does a good job at it,” Agbayani said. “When he went out, I just told him, you’ve got to be the best and be able to compete. This is what it’s all about, right here. Finish it.

“I tip my cap to Ishigo. He does a really good job with them. He’s always in the state tournament. He always leads that East. Kailua’s always been competitive and he always gets them ready,” Agbayani added.

Zayne Hookala was the hard-luck starting pitcher for Kailua, leaving after 42⁄3 innings with four runs — two unearned — on his ledger. He fanned two, walked four and allowed three hits.

“Zayne did an outstanding job,” Ishigo said. “We tried to leave it all on the field for Burgo tonight. He’s our one senior and we did it all for him.”

Kaimana Burgo took the loss, Kailua’s leadoff man and left fielder took the mound for the bottom of the sixth inning with the game tied at 4.

In the seventh, Kahanu Martinez led off with a walk, then scored on Chun’s clutch double to left, giving Saint Louis a 5-4 lead. After Chun stole third base and Kaili Kane popped out, Yamaguchi singled through a drawn-in infield. Chun scored easily to give Saint Louis a 6-4 lead.

“It was a 3-1 pitch. I’ve got to give props to my (assistant) coach Trey Yuks (Yukumoto). We’ve been working on the swing and preparing for this moment,” Chun said.

Kailua went 1-2-3 in the bottom in the seventh, and Saint Louis celebrated one of its biggest comeback wins of the season.

The Crusaders won state titles in 1974 and 2014. They have been runners-up four times.

Kailua surged to a 4-0 lead in the first two innings, but Saint Louis refused to buckle. The Crusaders scored a run in the fourth and three to tie the game in the fifth.

Kailua (13-3) had eight hits in the first four innings, but struggled against Fernandez, who entered the game during the fourth in relief of Correa.

The Surfriders took command with three runs in the bottom of the first inning. Burgo led off with a walk, Hookala singled and Kaalekahi Kuhaulua’s bunt single loaded the bases.

Burgo scored from third on a wild pitch by Correa for the first run of the game.

After Masao Minami struck out and Rayvin Pagan walked to load the bases, Kalama Carreira delivered an opposite-field single to right, scoring courtesy runner Romeo Ortiz and Kuhaulua for a 3-0 Kailua lead.

The damage could have been worse, but Pagan was thrown out trying to advance to third base on Carreira’s hit, and Correa struck out Ryce Aoki to end the inning.

Correa did not pitch poorly, striking out three Surfriders in the first two innings. Kailua was simply and consistently on point with perfect execution. In the bottom of the second, Jayden Hunt hustled for an infield single, went to second base on a sacrifice bunt by Sage Tokoro and came home on an opposite-field single to left by Burgo, opening Kailua’s margin to four runs.

Meanwhile, Hookala was in stealth mode. Saint Louis got its first hit off him with two outs in the third inning, an infield single by Martinez.

Saint Louis picked up momentum in the top of the fourth. Yamaguchi singled with one out and stole second base. Kolby Gushiken walked, and the two executed a double steal with Chase Sutherland at the plate. Yamaguchi scored his team’s first run on a sacrifice fly to center by Sutherland. On the first pitch to Kaisa Lemau, Gushiken was thrown out by Carreira, Kailua’s catcher, while attempting to steal third, ending the inning.

Kailua had runners on third and second bases in the bottom of the fourth when Fernandez replaced Correa. He retired Kuhaulua on a grounder to first for the third out.

Saint Louis reached Hookala for two runs in the top of the fifth. With Lemau at third base and Mana Heffernan at first with one out, Lemau scored on a groundout by Martinez. Chun walked, and Kaili Kane’s grounder to third was muffed, then thrown away by Aoki. That allowed Heffernan to score, cutting the lead to 4-3.

With the bases loaded, DJ Kauahi replaced Hookala on the mound. Yamaguchi was intentionally walked to load the bases, but Kauahi walked Gushiken on five pitches, forcing Chun home with the tying run.

Sutherland’s fielder’s choice grounder ended the inning.

Kailua had a prime opportunity in the bottom of the fifth. With two outs, Carreira walked and Aoki’s grounder to second turned into a throwing error. However, Sutherland, the catcher, hustled to cover the play and snagged the errant throw on one bounce off the dugout fence. Aoki was caught off first base, and in the ensuing 2-1-6-2 putout, Carreira was thrown out at home plate to to end the inning.