[Notice] The SplatNet service for the Splatoon game on the Wii U system will be permanently closed on September 30th, 2017. Online multiplayer battles will still be available, as this update only affects the SplatNet service. We sincerely thank all players for using this companion site for the original Splatoon game.
— Squid Research Lab
Source: Splatoon’s Tumblr.
…Wanna play? Buy a Wii U.
And if you’ve already got yours, click on Splatoon for everything you need to know about the game. 😀