Sekiro: Shadows Die Twice - Every Ending Explained (And How To Get Them)
3. Purification - Ending Explained
Emma's research into the purification ritual is good news for Kuro, as it means that the process of severing ties with his immortality won't result in him dying. However, the reason she jumps around from place to place and requires so much eavesdropping is that she's discovered the procedure will actually kill Sekiro, and she's keeping it a secret.
In order for the purification to occur, those connected to the Dragon's Heir need to have their ties severed, in this case, Sekiro. After confronting Emma about this information, she'll concede that she hid the info because she wanted neither you nor Kuro to die. She relents at your request and gives you your father's memory to be used at the Buddah statue.
Upon returning to the Hirata Estate it's revealed that it was the Owl who stabbed you in the back all those years ago, and killing him drops the Everblossom. After combining it with the Dragon's Tears following the regular fight with Genichiro and Isshin, Sekiro kills himself with the mortal blade in order for Kuro to live.
The final cutscene shows the young Lord and Emma kneeling at your grave under a clear, sunny sky. Kuro promises to make every day count, and live how his Shonobi did for them.