Tanaka's fly to the warning track in left allowed Nobuhiro Matsuda to score from third. Toshiya Suguichi retired Taiwan in the bottom of the 10th for the save.
"There is nothing better than coming through for your teammates and fans when you get a chance like that," Tanaka said. "This was a huge win for us, and I'm glad I was able to contribute."
Japan will face the Netherlands on Sunday with a chance to secure a spot in the March 17-19 final round in San Francisco. Without any players on Major League Baseball rosters, Japan is attempting to win a third straight WBC title.
The Netherlands beat Cuba 6-2 on Friday. Taiwan must beat Cuba on Saturday to advance.
Taiwan took a 3-2 lead in the eighth when Szu-Chi Chou's singled scored Cheng-Min Peng from third. Hirokazu Ibata's two-out single scored Takashi Toritani from third from third with the tying run in the ninth.
Taiwan held a 2-0 lead through eighth inning before Japan tied the score with a two-run eighth.
"This was an entire team effort," Japan manager Koji Yamamoto said. "Our hitters came through when we needed them and the pitchers did a great job."
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