Key to accessing the True Ending
You cannot exit the room she is in, except by killing her. Five hits is enough to kill her, and then you will wake up in bed in the real world.
Demon Sabitsuki must be killed in order to access the True Ending.
- Whereas Rust's final, bloodiest form seems to only slightly resemble a red demon, Demon Sabitsuki outright looks like a red demon, due to the horns. Also, she is less bloody, only bleeding from the forehead and perhaps the mouth.
- It is possible that she represents Sabitsuki's weakened core.
- Her noticeable resemblance to a red demon suggests she has been corrupted due to Rust's control over Sabitsuki.