Two free kicks effectively secured the Japanese their second round place on Thursday but they could have scored more after dominating much of the match.
Olsen, however, was in no mood to pay tribute to the Asians afterwards at the Royal Bafokeng Stadium.
"It was not a matter of a good Japan or a poor Denmark, it was just unnecessary what happened," he told a news conference.
"Beforehand I underlined the importance of the first goal and when (Keisuke) Honda struck it became an uphill struggle for us.
"We knew that they had two players who could execute and we couldn't prevent it," he added.
"We started well tonight, created the first chance and that gave us a good feeling but after the opening goal we were just chasing the game," skipper Jon Dahl Tomasson told Reuters.
"After the second goal it was all over."
