Fighting Owl Twice
How did the second fight with Owl at Hirata Estate happen? This is supposed to be a memory of what happened 3 years ago, but the two memories are contradictory. The first time, after you fight Lady Butterfly, Owl stabs you in the back, forcing Kuro to save you by imbuing you with the Dragon's Heritage. The second time, you fight Owl himself in the same place and defeat him. Both memories cannot be accurate if they happened at the same time, but other events depend on both being canon. If Owl backstabbed Wolf, then Wolf couldn't have fought Owl at all. But if he didn't, then Wolf never died and thus never needed the Dragon's Heritage. Can this just be chalked up to Timey-Wimey Ball?- The memories are not literal. It's some sort of metaphysical/spiritual experience where Sekiro literally relives the events that happened, and is able to interact with them in slightly different ways. The first memory is the memory of Sekiro himself (or maybe the old woman's witness account of these events), and ends with his death, the second memory is Owl's memories of the events after Sekiro's apparent death (the dialogue between NPCs makes it clear some time has passed). In the first memory, we're supposed to think it was a mix of actual events (Sekiro's interaction with the robber, who later recognizes him, for example) with made up stuff (Sekiro using a prosthetic arm he didn't have yet, and skills he hadn't learned yet). The second memory already starts after Sekiro is dead, so none of his interactions actually happened, it's all his own perception of the events.
The One Who Keeps the Mortal Blade
Why does the Divine Child of Rejuvenation have the Mortal Blade? Was it entrusted to her by the monks? If so, why would they give her the one weapon that could be used to end her life should she feel like she didn't want that kind of existence for herself anymore?