Can I Log Into My Nintendo Network ID on a Different System?
Nintendo 3DS
A Nintendo Network ID can be linked to one Wii U and one system in the Nintendo 3DS family. This means that it can be created on a Wii U and then linked to a Nintendo 3DS, or vice versa.
It is not possible to link the same Nintendo Network account to multiple Wii U or multiple Nintendo 3DS family systems at the same time.
Wii U Transfers
Once a Nintendo Network ID has been associated to a Wii U, it can be moved to a different Wii U by using the Wii U Self-Service Transfer Tool.
Nintendo 3DS Family
Once a Nintendo Network ID has been associated to a Nintendo 3DS, it can be moved to a different Nintendo 3DS by performing a System Transfer.