Sekiro’s Hirata Estate is visited twice: once through a standard memory access, and once through a hidden second memory unlocked by giving the Immortal Severance item to the Old Hag in Ashina Castle. The second memory shows the same estate on the same night but hours later — and the enemy layout, boss, and environmental details are completely different.
The first Hirata visit shows Owl’s betrayal of Kuro. The second shows what Owl was doing while Wolf was occupied: a second betrayal, of a different kind, against a different target. The two memories together form a complete picture of the Night of Three Fires that neither shows individually.
FromSoftware built the second Hirata memory to be entirely missable — it requires a specific item that is easy to sell, given to an NPC that is easy to kill, in exchange for a memory that players with no foreknowledge would have no reason to seek. Players who found it without a guide did so through the combination of item-description reading and NPC patience that characterises Fromsoftware’s most dedicated explorers.

Currently on my first run and now I have to go back and look for this. Worth the detour.
Found this by accident on my third run. Came here to understand what I was actually looking at. Great write-up.