Rocket Company released a software update for Medarot DUAL on December 18th in Japan. Patch 1.1 fixes a bug that saw a connectivity error after certain battles in the story mode. Additionally, the patch provides support for downloadable content released after December 19th, 2013.
To initiate the download simply scan the QR codes with your 3DS in the Camera app. The patches are custom tailored for each version of the game, so make sure you scan the code that matches up! A firmware update for your 3DS may also be required.