Sekiro: Shadows Die Twice seems to be a well-optimised game as its PC system requirements are fairly low. The 25GB required disk space may not even be initially required as PlayStation 4 download is almost half that size before DLC.
Sekiro: Shadows Die Twice is the highly anticipated game by FromSoftware due to Dark Souls 3 being the last entry in the series of hard games specifically tailored for hardcore players with high skill ceiling or masochists who like seeing the "You Died" screen a lot.
Thankfully, the PC hardware ceiling won't need to be that high. The minimum requirements list an i3-2100 or AMD FX-6300 CPU with 4 GB RAM and GTX 760 or Radeon HD 7950 GPU. This is the low end of PC hardware these days and the cost of such a rig would be even lower than that of a mainstream console these days.
Sekiro's recommended PC specs aren't that high either, with i5-2500k or AMD Ryzen 5 1400, 8GB RAM and GTX 970 or RX 570. This configuration can probably be classified a medium-grade PC and the cost of one could match the cost of a PlayStation 4 Pro or Xbox One X, provided you go down the AMD route as Intel and Nvidia hardware has a bit steeper price.
Should these system requirements prove to be correct, Sekiro will likely be praised for some of the best optimisation in modern day gaming.
Meanwhile, the disk space requirement is low across the board. The aforementioned system requirements that were picked up from Steam mention 25GB of necessary disk space but latest info suggests that the game will initially take up just a fraction of that size with measly 12.5GB on PlayStation 4 .
System requirement section on Steam probably accounted for post-launch content which could increase the size up to 25 GB and PlayStation 4 users mentioned a 3.6 GB day one patch. FromSoftware certainly did their best to put the 100GB+ giants to shame.