Maeda was coming off a subpar performance against Australia in an exhibition game, but rebounded in a big way, limiting China to one hit and striking out six over five scoreless innings to pick up the win.
"I had a week since the last outing, so I was able to make adjustments," Maeda said.
Japan will have the next two days off, with Cuba as the last remaining obstacle between them and the top spot in Pool A. Japan faces Cuba on Wednesday in a game that can be seen live on MLB Network and ESPN Deportes.
"We're in good shape," Japan manager Koji Yamamoto said. "I wish we could've scored a little earlier, but I'm satisfied."
hinese starter Xia Luo, 20, was the losing pitcher, but had a surprisingly good outing, holding Japan to one run over 3 2/3 innings. Luo, who struck out two and walked two, was forced to leave the game in the fourth after reaching the first-round's 65-pitch limit.
"He was moving the ball around and he was changing speeds," China manager Jon McClaren said. "He was getting ahead of them, and when you get ahead, I don't care what level you are."
Luo's night was even more impressive considering no one -- least of all the pitcher himself -- expected him to take the mound.
"He didn't know until game time he was pitching," McClaren said. "He probably heard on the Internet. We shuffled our pitching around a little bit. He stepped up to the plate and did a great job."
Japan's fortunes changed when Luo was the bench and reliever Dawei Zhu on the mound in the fifth. Seiichi Uchikawa burned Zhu for an RBI single early on, and Yoshio Itoi added a three-run double.
"This was a do-or-die game, and I'm glad we won," Itoi said.
Unlike the Chinese, Japan's relievers didn't run in too many problems. Tetsuya Utsumi, Hideaki Wakui and Hirokazu Sawamura were perfect over the sixth, seventh and eight innings, combining to strike out six over that span.
Japan's final pitcher, Tetsuya Yamaguchi, ran into trouble in the ninth, giving up two runs while allowing a pair of singles and throwing two wild pitches.
Shortstop Ray Chang, who was the hero of China's victory over Taiwan in the 2009 Classic, finished 0-for-4 and drove in a run in the ninth on an RBI groundout. Lei Li accounted for the Chinese's lone extra-base hit when he connected for a double off Maeda in the fourth.
"Team China is young and we don't have much experience," Li said through a translator. "We have very limited opportunities and have players who are a little nervous, but we never gave up during the game."
Luo had one of his few missteps when he walked Itoi with one out in the second. Itoi stole second, took third on a groundout by Hisayoshi Chono, and scored on a two-out single to left off the bat of Sho Nakata.
Nobuhiro Matsuda led off the fifth with an infield single and advanced to second on Hayato Sakamoto's sacrifice bunt. Kazuo Matsui drew a walk to put two on, and Uchikawa singled to right to score Matsuda from second, making the score 2-0.
Shinnosuke Abe then drew a walk that loaded the bases, and Itoi cleared them with his double to center, making the score 5-0.
Meng Weiqiang and Cui Xiao singled to start the ninth. And after a Delong Jia strikeout, the pair advanced a base when Yamaguchi threw a wild pitch to Li.
Yamaguchi struck Li out on another wild pitch, but Li made it safely to first while Meng scored and Xiao went to third. Chang's RBI groundout brought in another run, before Yamaguchi struck out Wei Dong to end the game.
China is scheduled to face Cuba on Monday at 4:30 p.m. locally and 2:30 a.m. ET.
Jason Coskrey is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.