North America already has the game, and the Japanese wait isn't much longer.
3D Classic Kirby's Adventure is releasing on the Japanese eShop on April 25, according to Nintendo at their latest Nintendo Direct presentation.
3D Classic Kirby's Adventure released in North America last year. The Japanese version of this game is finally on the way. You can read a review of 3D Classic Kirby's Adventure here.
The announcement that the 3D classic version of this game would be finally releasing in Japan was accompanied by an announcement of a new Wii Kirby 20th anniversary collection.