Celtic midfielder Shunsuke Nakamura put the visitors ahead with a 17th minute free-kick, Yasuhito Endo doubled the advantage from the penalty spot shortly before the break before Kengo Nakamura's deflected strike extended the lead with six minutes remaining.

But Japan endured a nervous final few minutes as Salman Isa and an own goal by Marcus Tulio Tanaka cut the deficit to just a single goal.

"I'm delighted that our players worked hard in this heat to collect three points," said Okada.

"We panicked during the last 10 minutes when we gave away two goals. But this could be a best way to win the game for us as, more than the goal difference, we were able to learn something from the game.

"The outcome of the game can change with a small mistake.

"If you lose your focus, this can happen. On top of that, our substitute players didn't fulfil their duties. It's football."

Meanwhile, Okada's opposite number Milan Macala was critical of his side's performance.

"I'm not happy about this result," said the Czech, who led Bahrain to a 1-0 over Japan at the same venue six months ago.

"Japan didn't create one opportunity at all but we helped them with mistakes.

"We lost the game because we didn't play well in the first half. This is our problem. We came on to the field with a big respect for Japan. I don't know why.

"You know our experience from the last time when we beat Japan. We said we were changing. Our spirit was out there.

"But what I saw was different people and different reaction from my players. Once it was 1-0, they controlled the game better and this created psychological problems for us."