you can just give her the JP CIA and you can play wireless locally. i believe MK7 is international.I have a US 3DS and I have a friend with a Japanese one. I'd like to play MK7 wirelessly with her, so I gave her a US cia and put a file in the locale folder forcing USA EN. Unfortunately the Japanese 3DS always says there's some error when she tries to connect wirelessly.
Is there a solution, or is this basically a lost cause?