Splatoon 2 seems designed to be played with friends, but it also supports playing offline and alone. If you cannot play your game online, there is still a single-player component you can access if you have the game.
How to access single-player missions in Splatoon 2
You can start the single-player missions in two different ways, depending on which set you want to play. For single-player missions that were available at launch, contact Marie. Marie is the person with the yellow-green umbrella in Inkopolis square. When you get close, she’ll go into the drain so just press ZL to go into the drain after her. She will give you missions to do.
The second method comes with the Octo Expansion DLC released in 2018. You must enter the back alleyway in Inkopolis Square to begin these missions. The Back Alley is right next to where Murch is sitting. Go to the gated underground and press the A button when you see the prompt Listen Closely… This will start the single-player expansion missions.
Can you play Splatoon 2 in Split Screen mode/local multiplayer?
Splatoon 2 does not support split-screen play or offline multiplayer. To play with friends, you will need a Nintendo Switch, a copy of Splatoon 2, and the ability to play online. This is something that may be added in Splatoon 3, but we won’t know until it’s out.
For more on Splatoon, check out Splatoon 2: How to Add Ability Slots and Reroll or Does Splatoon 3 have Single Player Mode? here on Pro Game Guides!