Ao Oni is an adventure horror game created by noprops.
The story about the boy named Hiroshi, who is trapped with his friends, investigating a deserted mansion that is rumored to be haunted. Upon entering the mansion you and your friends discover that the mansion is haunted by a mysterious creature named the Ao Oni (青鬼 in Japanese, literally "Blue Demon") a tall creature with a deformed face that proceeds to chase you and your friends through out the mansion. Sealing all exits.
There are four different versions of the game, each with their own puzzles, maps and endings. Only the two lastest versions have been officialy translated.
Versions, from 1.0 to 6.23
The original version of the game, highly different from the following ones. It was only released in japanese. It features the most characters, and most of them having different personalities and appearances than their later counterparts, while other characters are completely erased.
The game begins when the protagonist, Hiroshi, and his friend, Kazuya, are forced to go to an abandoned mansion in the outskirts of town with Takuro and his gang. Once inside, the kids hear a crash in another room, and Hiroshi has to investigate, only to find a broken plate on the kitchen's floor. Meanwhile, Takuro gets impatient and intends to ditch Hiroshi there, but it turns out the front door is locked. Inmediatly after, the oni appears for the first time to chase them, and the group splits up when running away and hiding. As Hiroshi comes back and finds himself alone, he begins to search for an exit and a way of getting everyone out alive. The characters of Takuro and Ryota die, the frist one murdered by the oni and the second one's corpse is found in a bathtub, while Hiroshi, Kazuya and Megumi (Mika in the later versions) manage to escape alive. Takeshi, however, is found early in the game hiding inside a closet, and he never appears again, making his destiny unknown.
The second version to come out stablished the path the rest of the games would follow. Also released only in japanese. Hiroshi and his friends heard the rumor about a monster living in a mansion in the outskirts of town and decided to investigate, most likely for fun or curiosity. Like in the last game, the sound of something breaking can be heard, and Hiroshi heades to investigate, finds a broken plate in the kitchen and goes back to report his findings, only to see that his friends are nowhere to be found and the front door is locked. While searching around the mansion for an exit, he is chased by the oni several times, while his friends die one after the other.
The very first version to be officially translated into english, 5.2 again drastically changed maps and objects, yet kept the premise and characters identical. However, the events concerning their fates change, as there are no death scenes, and it's possible to rescue your friends before escaping the mansion. This version stands out for having the Abacus puzzle, difficult for westerns players as it involves a japanese abacus. It also introduces Leechum or Roach Oni.
The last version of the game, and for now the definite one, translated into English and Italian. Once more, the premise is exactly the same, but changing many of the elements: your friends turn into onis themselves after they die, a new whole building is introduced, Roach oni is replaced by Blockman and it is possible to change Hiroshi's name or use this feature to insert codes that modify the game itself, between other things.