It was a sunny day, just like any other.

As usual, Guest woke up at dawn and went for a walk on the mountain near the house. Perhaps because it had rained yesterday, the mountain was covered in thick fog, but it wasn't so bad that one would get lost. At least, that's how it seemed at first.

When Guest reached the midpoint, the mountain was suddenly enveloped in fog, becoming incomparably darker and murkier than before.

Eventually, Guest decided to turn back, but finding the path was difficult due to the fog. Guest decided to rest by a nearby tree until the fog cleared.

While fumbling for a tree, what Guest's hand touched was not bark, but a door. A massive door, at that.