Japan close in on Olympics quarters. Could South Korea join them?

Lee Kang-in netted two goals in the final six minutes to seal a commanding 4-0 win for Korea Republic over Romania in Group B of the Olympics men's football tournament on Sunday. AP Photo/Fernando Vergara

It was a day of mixed fortunes for Asia's representatives in the men's football tournament at the Tokyo Olympics.

While Japan and South Korea both claimed potentially crucial victories, Saudi Arabia and Australia fell to defeats -- one of which proved extremely costly.

We take a closer look at how the Asian Football Confederation's four Olympics contenders fared in Sunday's second round of fixtures.

South Korea up and running in emphatic fashion

Having lost to New Zealand in their opening match, the South Koreans were in desperate need of a win in order to keep their hopes of reaching the quarterfinals alive.

They duly delivered with a 4-0 rout of Romania although they did receive some help from their opponents, with a Marius Marin own-goal breaking the deadlock in the 27th minute before Ion Gheorge was sent off right before halftime.

With the numerical advantage, South Korea went on to produce a professional and clinical display in the second half as they piled on three more goals, including two in the final six minutes from Valencia's budding star Lee Kang-in.

Lee is widely regarded as one of Asian football's hottest properties but still needs to add another level of consistency to his game, and it was not completely a surprise that he started on the bench against the Romanians.

But he took advantage of his opportunity after coming on in the 79th minute and could play a huge role for the Taegeuk Warriors if can extend Sunday's cameo appearance to a full 90 minutes.

Samurai Blue walking the walk for now

After coach Hajime Moriyasu talked the talk with a bold pre-tournament proclamation that his team were targeting the gold medal, Japan are thus far walking the walk.

A 2-1 win over Mexico was particularly impressive, considering their opponents had beaten France 4-1 in the opening round.

Having struggled to break down South Africa in their first match before grinding out a 1-0 victory, the Samurai Blue shot out of the blocks on Sunday as they claimed a two-goal lead inside the opening 11 minutes -- through goals from Takefusa Kubo and Ritsu Doan -- that they would not relinquish.

Kubo and Doan have been tipped as the future of Japanese football, so it would have been a huge positive to see them play leading roles despite their relative tender years.

Australia still in the running but Saudi Arabia dream is over

There was little shame for Australia despite them losing 1-0 to Spain in Group C, considering their opponents' squad boasts six members who recently reached the semifinals of Euro 2020 with the senior side.

The shock 2-0 win they managed over Argentina on Thursday now looks all the more vital as they still sit second in Group C, knowing victory over bottom side Egypt on Wednesday will send them through to the last eight.

However, there was no such insurance for Saudi Arabia as a second consecutive defeat ended their hopes of progressing.

They can still be proud of the fight they showed in a 3-2 defeat to Germany, with Sami Al-Najei catching the eye with his two-goal display.

It looks like it could be a point-less campaign as they finish off on Wednesday against the mighty Brazil.