Sekiro: Shadows Die Twice only released two days ago, but it's already the fourth most played game on Steam and it's currently beating off Warframe and Rainbow Six Siege to secure a spot in the top five games for concurrent players.
Right now, there's upwards of 104,000 players taking on From Software's latest challenge, which - of course - doesn't even take those playing on console into account. According to Steam Charts (thanks, PC Gamer), it peaked at just over 124,266 concurrent players.
It's got some way before it breaks into the top three, though. While it's currently more popular than Grand Theft Auto V and Team Fortress 2, Sekiro sits 390K players behind third place Counter-Strike: Global Offensive, which is currently sporting 494,286 concurrents... and to knock Dota 2 off the top spot, Sekiro would need to notch up another 800K or so players. That said, it's a huge achievement for a primarily single-player experience.
As Wes points out, there's an interesting debate right now about the difficulty of Sekiro, and even From Software veterans are struggling with it. As Redditor KairoTheOwl says: "I'm doing my best to work with the new mechanics, but it feels like a total onslaught of my mind and soul from the beginning."