Captain and Liverpool midfielder Wataru Endo clocked a fourth-consecutive 90-minute appearance in Japan's round-of-16 win over Bahrain, while Arsenal defender Takehiro Tomiyasu made his second start after arriving in Qatar under an injury cloud.

That duo, plus Brighton's Kaoru Mitoma - who returned from injury against Bahrain - will miss at least one more league game due to Japan's quarter-final against Iran, and potentially two if they make the final.

When Endo does return to Anfield, it will be in the wake of manager Jurgen Klopp announcing his departure at season's end.

"Of course, it was big news," Endo said through a translator.

"I was a bit sad. But to be honest, it doesn't really affect me, performance-wise.

"All I have to do now is concentrate on my performances with the national team and try to win the trophy and bring back the winners' trophy to Liverpool."

The hard-working 30-year-old was adamant he could keep racking up the kilometres in midfield.

"My condition is actually getting better and better," he said.

"I am the captain of the team and I need to set an example. I need to be the leader of the team."

Chasing a first Asian Cup since 2011, the Samurai Blue appear to be hitting their straps at the right time after finishing runners-up to Iraq in their group.

Goals from Ritsu Doan, Takefusa Kubo and Ayase Ueda ensured a comfortable 3-1 win over Bahrain on Wednesday, and with it passage to the round of 16.

Tomiyasu, though, wants more.

"I was injured but I'm fit now. I missed the first game but ... my condition is getting better and better," he said.

"We are not in the best form now. We could have done better (against Bahrain). We should have done better, especially in the second half.

"We needed to kill the game after going 2-0 up, we gave them hope because they scored. We needed to manage the game better and close the game well.

"As a defender, I want a clean sheet every time I'm on the pitch. Today, we couldn't manage that. I'm not happy about it. But I'll try to keep a clean sheet in the next game."

Iran will pose a sterner test for Japan, who have conceded every game this tournament.

"Every opponent will come up against us, analysing us to try to find our weak points before the games. And they will try to expose us," Endo said.

"But I know that we have to make this right, we have to play with 100 per cent concentration for the 90 minutes."

Australian Associated Press