Surprise! To no one. Like Bloodborne and the Souls series Sekiro: Shadows Die Twice has multiple endings. Four to be precise. There’s the easy ending, the real ending, the true ending and the other ending that adds some extra lore. Those aren’t the real names. There’s the Shura Ending, the Purification Ending, the Immortal Severance Ending, and the convoluted Return Ending. Each has a few steps you need to follow to unlock it. Obviously, there are spoilers ahead.
Immortal Severance Ending
Up until the apex of Ashina Castle, you’re repeating the same steps as the Shura Ending. Play through the story until you beat Genichiro, Kuro will send you after the Corrupted Monk and the Guardian Ape, defeat these enemies then return to the castle to be confronted by your father. This time when you’re offered the choice forsake the Iron Code and side with Kuro. This will trigger a boss fight against the Great Shinobi Owl himself. Defeat him and Kuro will send you to an entirely new area. Playthrough this area until you defeat a pretty cool main boss and return to Kuro. Then you’ll be sent to the secret passage from the beginning of the game to fight the four-stage final boss. It’s a brilliant fight and winning it unlocks this ending.