It seemed like a scene from a spy movie -- wandering around back streets, nonchalantly surveying stores and faces, ducking into a small shop, and a swift exchange of cash. The entire transaction took less than two minutes and the object of this game? A device very much sought after by gamers in Japan -- the R4 Revolution for DS.

Slideshow: See the R4 up close

The R4, nicknamed "Majicon" in Japan, fits into the cartridge slot of Nintendo's popular handheld gaming device and allows games stored on a Micro SD card to be played on the DS. It has a been criticized for encouraging piracy but that, if anything, has only increased gamers' desire for it.

In gaming circles it's been well-known for a while but those that didn't know about it were clued in a couple of weeks ago when Nintendo and most of Japan's biggest software makers filed a lawsuit against five companies for importing and selling the device.

As a result shopkeepers with stock became skittish about overtly advertising the device and these days shopping for a R4 in Akihabara requires knowledge, connections, and sometimes even obscure passwords. There are no visible signs for it in the primary shopping streets, and when one inquires about its availability, store managers reply with a snappy no.

However, three intersections west of Showa-dori on the edges of the electronics district there remain retailers that are still selling it.

Venturing out with a gamer who prefers to remain unnamed, I saw how easy it was to get a hold of it.

"I already own three and now I'm here to buy for my Japanese friend", says the gamer. While the device is not illegal in Japan, its reputation as a catalyst for game piracy makes it a difficult and sensitive purchase.

Since Nintendo's lawsuit prices have risen. Back in July, an R4 and a memory card cost ¥5,000 ($45), but today this will only get you the R4 itself. However the price is still only equivalent to that of one DS game.

Sales figures for the R4 are difficult to come but if even a fraction of DS owners have bought one that could mean big sales.

As of June 2008, almost 23 million DS units that have been sold in Japan alone. But software sales in Japan have recently been flagging. In the April to June period this year there were about half that of the same period last year.

The IDG News Service is a Network World affiliate.