Demisexual isn't a word.
Here is the allowed terminology of the "sex" -words.
There are genders. Let's call them A,B,C,D,E,...
There is either ASEXUALLY reproducing organism or SEXUALLY reproducing organism.
If organism produces sexually it either
- produces ONLY with own gender and is called HOMOSEXUAL
- produces ONLY with another gender and is called HETEROSEXUAL
- produces with any gender and is called SEXUAL