① Result of sudden mutation. From the moment they are born, you can feel there is something different about them. A deviation from the norm in the family or group.
② In the world of Tsukihime, in which demon kind exist, the word demon-child doesn’t actually refer to the children of demons. Rather it is a discriminatory word carrying the meaning written above in ① In reality it has often been used to persecute humans with special powers.
③ “Demon-child” also has the meaning of “A child who doesn’t resemble his or her parents,” and the term was probably used to mean the same thing.

Translator's Notes
  1. ^ Oni Child.
Colorful MOON Tsukihime: Tsukihime Glossary