There are several examples of unused gameplay or graphical material within most Ao Oni versions. Sometimes, these materials are present in one version, but removed within the next.
There exists a number of unused graphical materials in Ao Oni. These unused sprites often suggest an unfinished portion of the game that was cut out, or a variation certain points in gameplay. Some of the unused assets appear to predate even version 1.1, due to Ryota appearing in them. suggesting that they possibly could've been used in very early stages of development.
A small number of audio tracks and sound effects exist in Ao Oni games. Most of these are simply Files from previous versions carried over to newer ones, but Version 1.1 had two unused audio tracks.
Version 1's Unused Tracks
The background music, "BGM0088.ogg," was also used in another popular RPG Maker game, Ib. Most likely stock music for RPG Maker.
The sound effect, "bikkuri.wav," is used only in Version 1.1 when the player discovers Ryota's dead body in the bathtub, but in future versions it was removed. The sound was taken from the visual novel Higurashi no Naku Koro Ni, which is in some ways similar to Ao Oni.
Not many things exist in Ao Oni's files that are unused, at least in the field of gameplay. An obvious unused portion is the fact that the characters have all had HP (Hit Points) and MP (Magic Points) since Version 1.1. This is because the game was created in RPG Maker XP, hence all characters have RPG stats. In Version 1.1 to Version 3.0, the menu screen also had such options as "Skills," "Equip" and "Status" which were removed in later versions.
One gameplay mechanic used in Version 1.1, that was taken out in later versions, is the amount of damage that will pop-up whenever the oni touches the player. This is due to the "battler_attachment" script which sets the function "self.battler.damage_pop" to "true" in Version 1.1. In future versions, it is set to "false."
Also in Version 1.1, there is one item in the game's data that was never used, the scissors (はさみ hasami ). It seems the player would find this item after Kazuya attaches the rope ladder to climb down into the underground tunnel, and during the time where Hiroshi and Megumi is heading toward the exit. The scissors were used to cut down the ladder in the final segment of the game. However, it was never implemented.