"Ao Oni S"(Also referred to as "Ao Oni: School Nightmare") is a Korean origin Ao Oni that takes place in Hiroshi's school, of which after receiving a call from his friend "Akira" telling him to come to the school as a dare. He quickly finds like in all Oni games that he is locked inside the building with seemingly no way out other than to solve puzzles.

It's note worthy that this game is a rarely known one, with even fewer players due to it's nature of being Korean. Most of it's puzzles require knowledge of the Korean language, otherwise you won't get very far in the game. Without such, your best luck is searching the internet for the puzzle answers, sadly it would take away from the experience if you're constantly having others solve the mysteries. A quick search from a search engine shows the game will yield very poor results with the only way to find out being YouTube videos of playthroughs.

Another note worthy thing is the difficulty of the game, even without the Korean. The Oni is much more frequent, spaces are much smaller and more narrow to get through. The Oni's usual chase theme is present, with some form of filter effects along with audio effects. There is an "Easy", "Medium", and "Hard"