All of the gameplay in Ao Oni takes place at a mansion (館 yakata ). Hiroshi describes this place as a "mansion on the outskirts of town." The estate includes a large house full of underground passageways, a large outdoor garden, an annex to the main house, and a separate building referred to as the "old building." In the beginning of Version 1.0 and the end of Version 5.2]], there are cutscenes which feature other locations, but the player is not allowed to move or explore.
The Mansion Edit
Most of the gameplay takes place in the front end of the mansion. This area has light wooden floors, whitewash walls, and is furnished like a normal house. Through each version, the layout and the sizes of the rooms change. Before Version 5.2, the mansion has four floors. Afterwards this was reduced to just three floors. The prominent rooms of the mansion include:
- The Foyer
- Nursery (A.K.A. Kid's Bedroom)
- Tatami Room
- The Shed
- Piano Room
- Archive Room (Removed in Version 6.03)
- The Attic
The Basement Edit
- Main article: The Basement
The basement is an area of the game present in all versions, but looks different in Version 5.2 onward. The new basement features darker floors and is completely rearranged, giving it somewhat of an eerie atmosphere.
The Annex Edit
- Main article: Annex
The annex was a new extension added to the mansion in Version 5.2, accessible through the basement. It features dark, red floors and appears to be in a state of decay. This area of the game features the doll puzzle and in Version 5.2, the roach oni.
The annex also has its own basement, separate from the earlier game area called "basement" and added in Version 5.2. The annex basement looks very similar, but has lighter walls and floors. This area features some puzzles like coloring puzzle (Version 5) and painting puzzle (Version 6). The Lattice/iron gate is located in the annex basement.
The Old Building Edit
- Main article: Old Building
The old building is the final area of the game, accessible only in Version 6. The building is separate from the main house and annex, and the player must walk outside and through the garden to get there. The Oni room and chapel are located here. The main puzzle of the old building is the blue jigsaw puzzle.
There is a scripted sequence in the library of the old building in which a Blockman Oni appears. From then on, the Blockman Oni may appear as a random chase.
- In the Ao Oni novel, the mansion is described as a Western-styled mansion (洋館 yōkan ) in which it was dubbed the "jailhouse" (ジェイルハウス jeiruhausu ).