Rust Corridor

^{Rust elevator}

The Rust Corridor (rust) is an area which can be accessed only by Rust. It leads to the Rust Ending.

Once Sabitsuki collects and discards all of the Effects, she becomes Rust, who can get empty item boxes in previously inaccessible areas. Gathering all three of them replaces the computer in My Room, in the flow, with the Rust elevator, which leads to the Rust corridor.

The corridor itself is linear, and consists of five sections, each more corrupted than the last. The player cannot return to the elevator from here. The fifth section of the corridor leads to the room which contains the Inner Demon. Rust equips the Iron Pipe upon entering the room, and she cannot leave. Beating the Inner Demon triggers the Rust Ending.

There are fourteen Fetuses in the area: one in the first section of the corridor, two in the second section, three in the third, four in the fourth section and four more in the fifth section of the corridor. There is no way to avoid being hit by them, and going through the entire corridor leaves Rust in her most damaged state.

Directions

My Room > Rust Corridor

Trivia

Rust theme plays in the background of this area. The last room's bgm is at a much lower pitch, and includes a heartbeat.
The player is transported to Sabitsuki's room after completing this area. The effects of the Erosion Counter are removed from the room and the computer no longer works.

Theories

It probably represents Sabitsuki's or Rust's core, due to the final room resembling a body, and the Inner Demon in the room after it.
In section three, several mouths grow on the floor, in section four the growths seem to form into red heads with white hair and red horns, and in section five they transform into groups of three white-haired heads growing from a single source: one with a blank face, one with a large mouth, and the last one, behind the other two, with demon horns. This might be interpreted as Sabitsuki having three personalities or aspects: Sabitsuki herself, Rust, and the Inner Demon.