Sekiro: Shadows Die Twice was always intended to be a strictly single-player experience by FromSoftware. Now, a new fan-made mod on PC has made PvP and co-op gameplay possible.
You can check out the mod in action just below, in which the main player is invaded by an enemy player. This uses the 'Invasion' formula in Dark Souls as the foundation for the Sekiro mod, in which two players can duke it out until one is eventually defeated, and the invader vanishes back to their own game.
The mod itself is called Sekiro Online, and you can download it for yourself over at NexusMods. Posting over on ResetEra, the creator of the mod acknowledges that it's still "bit buggy," but it's still early days for the ambitious mod.
Sekiro Online enables both co-op and PvP combat. So aside from invading the games of other players to slaughter them, you can also hop into the world of another player to help them take out a difficult boss for example, just like you would do in many other FromSoftware games including Dark Souls and Bloodborne.
Sekiro: Shadows Die Twice has no online component whatsoever, which felt a little strange when it first launched in March 2019. Going from Bloodborne and Dark Souls, where the online aspect plays a subtle but significant role to Sekiro's complete lack of any online play whatsoever felt weird at first, but the game itself was still a triumph. We named it one of our best games of 2019 in our Game of the Year debate.