Well, that was quick. Real quick.
On April 11, retail shop Otacon Village was slated to open for business. The store, located in Osaka's geek area of Den-Den Town, featured two banners on the front of the shop that read, "R4, Majikon, TT DS".
As Kotaku posted previously, the R4 cartridge itself is not a piracy device; however, it can be used to play pirated Nintendo DS games. "Majikon" is how the device is referred to in Japanese.
A court injunction was filed in 2009 against Chinese R4 makers for "violation under Japan's laws". It's important to note that this legal injunction is for Japan only.
In late 2008, Nintendo (and 53 other companies) took legal action against the makers of the R4 cart, a device which allows, amongst other things, the pirating of games on a DS. Nintendo created an anonymous form for collect information about the sale of R4 cartridges in Japan. According to Nintendo, such devices hurts the growth of the entire game industry and steps must be taken regarding the legality of R4 carts.
Here is an image of the same Den-Den Town uploaded on April 14.
マジコンビルなう！あれ？ - tuskdon(tuskdon) [movapic via はちま起稿]