PMiSS netherworld

Illustration from Perfect Memento in Strict Sense.

The Netherworld (Meikai, lit. Gloomy World, 冥界) is the land where ghosts reside after death. Apparently it's a distinct part of Gensokyo, but is separated from the Land of the Living by a strong barrier (one even Marisa couldn't breach with her raw power).

The barrier is situated at a great gate high above the clouds. Unfortunately, like most barriers in Gensokyo, this barrier is rather vague, and, while it's powerful enough to keep people from passing directly through, there's nothing preventing people from flying over it. Thus, the Border between Death and Life is quite thin. Depending on the scenario, the barrier was either taken down by Reimu (Reimu's story), flown over (Marisa's story) or simply bypassed (Sakuya's story).

During the events of Perfect Cherry Blossom, the barrier was weakened by Yukari Yakumo and had to be repaired by her afterwards. Apparently, she never got around to repairing it, as the boundary continues to thin in the summer of Imperishable Night.

The Netherworld was the location of the first stage in Ten Desires.

Hakugyokurou is located in the Netherworld.