A goal from Keisuke Honda in the 39th minute proved the difference between the sides at the Free State Stadium.

Le Guen had opted for an adventurous 4-3-3 formation but his side struggled to create any meaningful opportunities and could not break down a resolute Japan defence.

The closest they came to finding the target came five minutes from time when Stephane Mbia's effort hit the bar, and with the talismanic Samuel Eto'o tightly marked it was a frustrating afternoon for the African side.

Le Guen's aim going into the tournament had been to try and emulate the team of 1990 that reached the quarter-finals.

However, with Holland winning earlier in the day in the group, his side face an uphill struggle.

Le Guen said: "Of course I am upset that we have lost the game but our attitude was wrong.

"We were tense and nervous, especially in the first half. We did not show what we are capable of. We were not at our level and kept losing possession."

Japan's goal came as the result of poor defending when Cameroon failed to cut out a cross from Daisuke Matsui.

Honda reacted quickly at the back post to finish well and Le Guen said: "My players were wrongly positioned."

It was little wonder the CSKA Moscow midfielder enjoyed the moment as he celebrated his 24th birthday yesterday.

Honda's star is rising as he sealed a move to Russia at the turn of the year after playing for modest Dutch side VVV Venlo and he helped CSKA reach the quarter-finals of the Champions League.

Honda said: "I had to stay calm when the ball came to me as we have missed chances in recent games.

"It is not just about me, however, we defended well. Our team has not had good results but we got it right when it mattered."

Japan arrived in South Africa without a win in five warm-up matches, scoring only one goal.

But coach Takeshi Okada could afford a wry smile after the game.

He said: "We knew Cameroon would be physically strong and so it proved. But my players had a strong motivation to do well.

"They asked me before the match if they could stand with shoulders linked at the national anthem. I thought it was a good idea."