Amiha's Nightmare Castle Walkthrough
Enter the room to your right. Interact with the closet door. After the cutscene, leave the room and start running down the looping hallway. After about ten seconds turn back. Interact with the blood-spattered window to save if you want to. You can now walk to the end of the hallway and through the door.
You will now be in a nexus-like area with four entrances. You can enter them in whatever order you like. Each room contains puzzles you have to answer to get the ending.
North Room
Enter the top-left door. Interact with the unlit lamp then leave. Interact with the door in the middle. Interact with the unlit lamp on top, then with the one on the right.
East Room
This room has four shelves with yellowing shining objects on two of them. Interact with the shining object closest to the right. Interact with the shining object to your left. Go right and interact with the unlit lamp.
South Room
Interact with the pillar in the middle. Enter the door that appears behind you. Interact with the unlit lamp to your left.
West Room
There are three doors you can interact with, each of which will call out a variation of your character's name. Answer Yes to the door that says "Mae?". Interact with the unlit lamp.
Ending
Enter the Northern Door. Interact with the shining object. Answers to the questions:
Room E: S
Room W: N
Room S: W
Room N: E
The game will end after some dialogue.