Japan will face hosts Qatar in the quarterfinals of the U-23 Asian Cup after a 1-0 loss to South Korea on Monday consigned Go Oiwa's men to a second-place finish in Group B.
Kim Min Woo's 75th-minute header secured South Korea first place and a meeting with Indonesia in the last eight of the Olympic qualifying event, which will send the top three teams to the men's football tournament in Paris.
Japan and South Korea had both won their two previous games, leaving them with identical records coming into their group-stage finale.
"We'd love to have won but will look to switch our focus as we have the next game coming up," said Oiwa, whose team is bidding for Japan's eighth consecutive Olympic appearance.
"I believe it will be a tough game whoever we face once it gets to the knockout stage. We'll prepare with that assumption."
Winger Yu Hirakawa's shot from 25 meters out whistled past the post midway through a first half dominated by Japan, who dealt with two counters from South Korea heading into the break at Jassim Bin Hamad Stadium.
Things began to heat up early in the second half after Kim Dong Jin's high tackle earned the South Korea midfielder a yellow card and sparked a scuffle between the two sides. Substitute Kim Min Woo broke the deadlock when he headed in from a corner.
Japan keeper Taishi Brandon Nozawa denied Kang Seong Jin's shot creeping inside the near post before Kein Sato sent his shot bouncing over the bar from close range. The Japan forward also had a chance to level in stoppage time but fired his header against the post.
The fourth-place finisher in Qatar will have a chance to qualify for the Olympics via a playoff with Guinea on May 9 in France.
