The weekly sales information for games released in Japan was announced today and Pokemon Fushigi no Dungeon: Sora no Tankentai topped the charts. It was the top selling game for the week of April 13th to April 19th 2009, selling 141,771 copies. Considering the game was only released on April 18, it sold quite a few copies in a matter of days.
Source:
http://www.m-create.com/ranking/