Japan edged out Cameroon 1-0 in a low quality game at Bloemfontein's Free State Stadium which produced little in the way of goalmouth action.
A half full stadium witnessed two out-of-form teams struggle to find any inspiration in another tepid World Cup encounter.
After a dire opening half-hour the Japan took the lead against the run of play when Dalsuke Matsui's cross looped over Stephane Mbia and was met by Keisuke Honda, who sloted home from six yards out at the back post.
Cameroon almost earned a point with two late efforts when Mbia hammered a stunning effort towards goal from 25 yards which crashed off the crossbar in the 85th minute and following that Kawashima saved from Pierre Webo in injury time.
Based on the opening round games, we will see the Netherlands and Denmark qualifying from this group.