Japan caused a minor upset in Group E as Keisuke Honda scored the only goal of a hard-fought game against Cameroon.
Cameroon go down 1-0 in Bloemfontein
Japan caused a minor upset in Group E as Keisuke Honda scored the only goal of a hard-fought game against Cameroon.
Chances were few and far between in the first half but Japan managed to edge in front seven minutes before the interval when Honda netted from a Daisuke Matsui cross.
Cameroon battled hard in the second period in an effort to get back into the game but could find no way past a disciplined Japan back-line.
Stephane Mbia did almost equalise with a ferocious shot against the crossbar late on but Japan held firm to prevail 1-0 and Cameroon now face an uphill struggle to advance from a pool that also includes Holland and Denmark.
Cameroon manager Paul Le Guen stayed true to his word and made a couple of surprising selection decisions, with Schalke teenager Joel Matip starting in place of Arsenal's Alex Song in midfield and Hamidou Souleymanou preferred to Carlos Kameni in goal.
But both sides were slow to settle and relinquished possession far too easily, with most attacks breaking down due to a careless pass rather than a well-timed tackle.
Urgency
Japan's defensive organisation made it difficult for Cameroon to carve out opportunities, but they were reluctant to commit too many men forward themselves in a turgid stalemate early on.
Pierre Webo looked to inject some urgency into proceedings with a forceful run down the right wing, although his low cut-back was just behind Eric Choupo-Moting and the danger fizzled out.
A free-kick appeared to be the most likely source of a goal as both keepers struggled on crosses, with Eiji Kawashima landing painfully on his back after getting into a tangle with one high ball.
The game finally started to open up as half-time approached and Kawashima was forced to make a routine save from Eyong Enoh after good build-up play involving Benoit Assou-Ekotto and Choupo-Moting.
The deadlock was then broken at the other end moments later as CSKA Moscow midfielder Honda, playing in a more advanced role, escaped from his marker to control Matsui's excellent left-wing cross at the back post and finish past Souleymanou.
Cameroon had to regroup at half-time and immediately won the first corner of the match after the restart, while national legend Samuel Eto'o began to get on the ball more and embarked on one dazzling dribble before setting up Choupo-Moting to shoot wide.
Mbia, partly at fault for Honda's goal, gave away a free-kick just outside the area for a clumsy challenge on the skilful Yoshito Okuba, although Cameroon were not punished as Yasuhito Endo's delivery struck the defensive wall.
The Indomitable Lions shrugged off that scare and continued to press forward in pursuit of an equaliser, with the lively Choupo-Moting driving an effort wide from distance after cutting in from the left.
Onslaught
Achille Emana was introduced as an attacking substitute just after the hour mark and Geremi and Mohamadou Idrissou were thrown on 10 minutes later.
Japan dropped deeper and deeper to protect their lead but coped well with the mounting onslaught, restricting Cameroon to long-range strikes and the occasional set-piece.
Takeshi Okada's men almost moved 2-0 in front on a rare venture into the opposition half when Souleymanou made a sprawling save from Makoto Hasebe, although the flag had already been raised for offside by the time Honda followed in on the rebound and hit the post.
The woodwork was then rattled at the other end as Mbia came agonisingly close to salvaging a point for Cameroon with a powerful, swerving piledriver that ricocheted off the bar.
Kawashima then made a stunning save to deny Webo, not knowing the whistle had already gone for a foul in the box in Japan's favour, as his side clung on to claim three vital points.
