Despite not being expected to launch until next year, Nintendo’s new (appropriately titled) Nintendo Account system is open for registration in Japan.
Nintendo Account serves as the replacement for Club Nintendo and will serve as a unified account system for Nintendo devices, smartphones, and PCs. While details are still limited as to how exactly this will come into play with the NX, it does seem that, for now at least, Nintendo Network IDs are still a thing.
You may use your NNID, as well as Twitter, Facebook, Google Plus, or email address to register for a Nintendo Account.
In addition, Nintendo is running special promotion: for every 1,000 yen spent on the eShop until February 1, account holders will receive a coupon code for 100 yen off a future purchase.
Right now, Nintendo Accounts are limited to Japan, and no details have been released about a rollout in other regions.
Source: Nintendo of Japan