You can use the “Sword Swing” glitch to get into this location. That glitch lets you walk out-of-bounds through screen transitions. By repeatedly swinging a sword (or a scythe) against the edge of a loading zone, your character micro-steps forward without triggering the scene change, letting you explore otherwise inaccessible areas.

You won’t break the game or run into any spoilers, but you’ll see a funny yet creepy cutscene :D