The mansion is easy to get into. That's the first thing. The door is just open.
Hiroshi goes in first, because Hiroshi is the kind of character who goes in first. He calls back to the others: it's fine, come on, stop being scared. The others follow because they always follow.
Inside: locked rooms, puzzles, the architecture of a building that has too many interior walls to make sense from the outside. The usual logic of the horror game — you are meant to explore, to find keys, to open doors, to go deeper.
Then the creature appears.
It is blue. It is roughly humanoid. Its face is wrong in a way the pixel art conveys with remarkable economy — just a few white circles for eyes and something below them that isn't quite a mouth. It moves faster than you want it to. It comes from directions you weren't watching.
Ao Oni is a chase game as much as a puzzle game. You run. You hide in closets and under beds and behind doors and you watch the blue shape patrol through the room you are hiding in, and you count seconds, and you breathe carefully, and you wait for it to leave.
The puzzle solutions are logical once you find them. Each room has what it needs somewhere in the mansion. The game is fair, as horror games go.
Except for the notebook.
The notebook appears partway through the game in a room that was previously empty. It is a composition notebook. It contains, in handwriting that belongs to none of the characters you're playing, the solutions to the puzzles ahead.
Not the puzzles behind you. The ones ahead. The ones you haven't reached yet.
There is no explanation for the notebook. No character comments on it. Hiroshi picks it up and uses it the way you'd use any found item — as a resource. The game treats it as ordinary.
You are meant to understand, without being told, that someone else was here before you. Someone who made it far enough to write down what they learned. Far enough to leave a record.
You are not told whether they made it out.
You are not told what happened to them.
The creature continues to hunt you through the mansion. The puzzle solutions in the notebook are correct. They keep being correct, room after room, as though whoever wrote them wanted very badly for the next person to get further than they did.
There are multiple endings. In several of them, the creature is not stopped.
In the most common ending, Hiroshi escapes. The others don't.
He walks out of the mansion into daylight. He doesn't look back. The music is quiet.
You never find out whose notebook it was.
That's the part that stays with me. Not the creature. The notebook. The handwriting. The person who took the time to write it all down when they must have known time was something they didn't have much of.
They wanted you to get through.
I hope you make it.