DemonWPs (魔, Ma?) are those existences that, while being of the Laws of Nature (自然の法則, Jizen no Housoku?), distort the flow of such by the exercise of unnecessary powers. Covering both Energy and Magical beasts.
Demons represent both the use of magical energy (魔力, maryoku?), as well as the existence of Magical Beasts (魔獣, Majyuu?). The distortion that these cause to their surroundings is rather high, requiring them to be put down by existences such as the demon hunters. Yet they are not to be confused with Daemons (悪魔, akuma?) a more specific variety of existence.
There exists a variety of ways to become a demon. There are those who were given birth as a monster like Asterios, those heroes or gods who transformed into a demon in life like the Gorgon and those of a man-made demonic nature like familiars. Len is the best example of a familiar who has grown strong enough to be considered a demon by acquiring the ability of a succubus. Humans by losing their humanity due to their own actions or by the actions of others are also capable of becoming Demons, for example by becoming Vampires.
 Colorful Moon Tsukihime: Ma
① Demons are a part of the law of nature itself, but their existence is unnecessary to nature since their demon powers distort the flows of natural power.
② Their existence itself is distortion, so demon hunters move to exterminate them as soon as possible.