Oni Child

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 oni kind exist, the word oni-child doesn’t actually refer to the children of oni. 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 “Oni-child” also has the meaning of “A child who doesn’t resemble his or her parents,” the term was probably used in a similar manner to this.

Colorful MOON Tsukihime: Tsukihime Dictionary