The world is split in two. The human world, the world of science, continues on unaware that a second world, a land known as Gensokyo, is forever linked with it yet apart from it. The divergence left Gensokyo sealed away by a mystic barrier, holding within it the flights of fancy, imagination, magic, and mysticism that the human world had outgrown. In this land, youkai and sorcerers live together, ancient princesses walk alongside normal humans, and faeries play with spirits of the seasons.
The seal to the human world is maintained by the Hakurei Border, and the gate between the two worlds is located in the Hakurei Shrine, whose Maiden maintains the balance to keep both worlds healthy. Just as in any other land, Gensokyo has individuals with desires for more, or arguments between beings. Most are solved non-lethally with the use of Danmaku, a magical ritual fighting style, but not all are settled this way. There is some interaction between the worlds, and many youkai are fascinated by human technology, but rarely do the magical beings cross over to the other side.