The cartridge slot on the Genesis 1, 2, and CDX is different from that of the Japanese Megadrive. Japanese cartridges are rounded on the ends, so you won’t be able to get a Japanese cartridge to fit into the slotted and narrower cart slot on a Genesis 1/2/CDX. This can be taken care of by either using a pass-through cartridge or removing the tabs in your system’s cartridge slot. The software in the games also have some region lock-out code to keep them from playing. So naturally, we need to find away around these limitations.