So, the mystery hardware that Nintendo is expected to announce is actually an add-on cradle that adds a second control pad to the 3DS; the device is a cradle that the 3DS fits into that allows it to add the second control pad for true dual-stick control on the 3DS.

The add-on cradle device, which will apparently be called the “Expansion Side Port,” adds the second control pad to the right of the A/B/X/Y buttons once the 3DS is installed into the cradle. It is expected that Nintendo will announce a game or two that will offer optional support for the device; and one of these is expected to be a 3DS version of Monster Hunter, according to a source in Japan claiming to be in the know.

While the price is currently unknown, it is believed that this is the hardware that Nintendo will officially announce at the press conference that the company has on September 13th ahead of the Tokyo Gaming Show. Sources are suggesting that it will arrive in Japan first for purchase this holiday season and then become available in both North America and Europe very late this year, but most likely early next year.

While we have seen some pictures of the Expansion Side Pad, we have to say that it is a bit bulky and not at all something that we expected. We have to admit that we wonder why Nintendo didn’t see the need for dual-stick control during the design phase of the 3DS, as this is certainly an ugly way to add it now.