In the lobby of the school are two Kaibutsu. One of them is there by default, but the other only appears when the player has found at least one menu type within the game. (flower, orange, cake, etc.) Talking to the Kaibutsu allows the player to change which menu he or she is using.
There is also a room at the lowest level that is inaccessible until the time comes for you to shed your effects and become Rust. When this happens, returning to this area is recommended.