You must have read the first 2 chapters of the light novel “Kumiai, Cookies & Genki Club” to understand this article.
In Kumiai’s universe, the magical creatures of tales and legends do exist, the different folklores around the world all have some truth to them.
There was a time when it was easier for these creatures to live close to humans, the magic was much stronger which allowed them to maintain a physical form in the human world.
Today this is not really the case anymore, the majority of these beings live in a sub-dimension of the Earth.
The Earth has a hidden side, a sub-dimensional twin to it where the magic once present on Earth is concentrated. Those who know call it the Mirror World.
The Mirror World is very similar to the Earth, but some parts of it are not necessarily in line with the evolution of the human infrastructure. For example, the island of Kumiai does not exist in the Mirror World, only the sea is present.
The most recent elements and places that are less steeped in extraordinary stories do not materialize in the Mirror World because for the magical creatures they “do not exist”.
The existence of magical creatures in the human world and their influence is greatly affected by human beliefs. The decline of fantasy people and creatures has been going on for several decades or even centuries now, at the time humans were more easily inclined to believe in the existence of these entities and magical phenomena. Nowadays, the evolution of cultures, technology and the drastic increase of populations make these beliefs disappear little by little, and the magical beings too.
It is almost impossible for a human to go to the Mirror World, with a few exceptions. Indeed, only a few chosen ones with strong mystical powers, like Sophie, can go through the “Cracks”.
The “Cracks” are anomalies that create a link between the human world and the Mirror World. Generally they are places that are quite isolated from the masses of people and are filled with powerful magical energy. It can happen that mini ”cracks” appear in densely populated places through the intervention of a powerful evil spirit.
Therefore, these “cracks” can only be opened naturally by the presence of a powerful point of concentration of magic or by the intervention of a magical entity from the Mirror World.
The lair in which the dragon Vaterschweigen (Shuu-chan) lived in a German forest was a Crack, he closed this “door” to the Mirror World before following Sophie.
Some sufficiently powerful entities are able to live with a physical form in the human world. This is rare nowadays because spirits and mythical creatures do not really find interest in living as humans in a world governed by absurd laws, but some of them, perhaps more curious or having found a certain satisfaction, live with us, hidden in the shadows out of sight or even among us in human form.
Finn and Shuu-chan are very powerful and therefore do not need to make much effort to stay living with Sophie.
Lynn was not supposed to be able to materialize but her powerful bond with Sophie gave birth to a physical form for the little fairy and is now able to live with her.