Goals from Yoko Tanaka and Mai Kyokawa proved enough for Japan despite Yun Hyon-hi’s reply and Korea striking the woodwork three times as they fell to their first defeat of the tournament.
The victory means Japan must only equal DPR Korea’s result in the final round of games, when they play hosts Vietnam, to retain the title they won two years ago and it also booked their place in next year’s FIFA U-20 Women’s World Cup in Uzbekistan.
In an open first period, both sides had chances to take the lead. Only six minutes in, a long ball eluded the Japan defence that Kim Un-hyang beat goalkeeper Sakiko Ikeda to. The winger’s touch took her wide but her cross eventually broke to full-back Yun Song-mi, whose superb 20-yard strike hit the underside of the bar and bounced out.
Two minutes later Japan should have gone in front but Kyokawa fired wide when one-on-one with the keeper.
The Koreans continued to look the more likely to break the deadlock with Kim Jo-ran missing a free header from five yards after great work by Kim Un-hyang.
And the unfortunate Yun struck the woodwork for the second time in the 16th minute when her free kick crashed against the bar, with Kim Jo-ran slicing the rebound wide.
Tanaka then had a great opportunity to double her tally when Kyokawa’s cross found her on the edge of the six-yard box but her control was poor and a defender blocked the shot.
In the 69th minute, Korea almost equalised when substitute Kim Un-hwa’s audacious 25-yard drive hit the frame of the goal with Ikeda beaten but the Japanese doubled their lead only three minutes later when a long ball found Kyokawa, who controlled well on her chest and fired past O Chang-ran.
The two-goal cushion lasted less than a minute, however, after substitute Yun Hyon-hi found space outside the box, switched the ball onto her left foot and fired a fantastic strike into the top corner.
The final minutes of the game proved frenetic, with Korea desperate to equalise and Japan dangerous on the counter, yet neither side could add to their tally as Hiroshi Yoshida’s side put themselves in a great position to win the trophy for a second successive time.