So my friend has some eShop credit left in his account, and I'd like to get Ryu, but I have no eShop credit. Can my friend buy Ryu then send me the code for me to use? Or is the code linked to the account?
The code can be redeemed by anyone as stated on the Nintendo eShop FAQ.
The code that you get when you buy any dlc can be used on any account but may only be used once.