Ao Oni (青鬼, Blue Demon) is a freeware horror and puzzle RPG video game. Until 2013, the game became an increasing cult popularity in Japan gaining notoriety on websites such as Niconico and YouTube where related videos exceeded 50 million views.
The player assumes the role of 'Hiroshi', a young teenager who enters a haunted mansion with his friends, Takuro, Takeshi, and Mika (Along with Kazuya and Ryota in the original). Shortly after entering the mansion, the doors lock behind them. Hiroshi doubts that the mansion is haunted, but soon finds himself being pursued by an enigmatic blue Oni. Hiroshi must now find a way to save as many of his friends as possible and escape the mansion alive.