Monster Hunter producer Ryozo Tsujimoto has explained how Monster Hunter 3 Ultimate for the Nintendo 3DS and Wii U will work together. To save data from both versions you’ll need to download a free app from the 3DS eShop, which you’ll use to transfer data from the Wii U to the 3DS, and from 3DS to Wii U. You can use your Wii U console and three Nintendo 3DS consoles to play four-player local co-op play over Wi-Fi. This feature is to make up for the lack of online play on the 3DS version.
“We wanted people to play together. We know there are some people who want to play online. Unfortunately with the 3DS version you can’t do that. But we have made this feature so you can play together. You can have your friends bring their save data to your house and have a Monster Hunter party. One person will play on the big screen and three other people will play with their 3DS versions. People can continue their save data from what they had before and go back home and update their data on their Wii U.”