you had volunteered for a program that included taking in one of the newly discovered breeds. In your case it was said that a succubus girl would come to you. It is said to be similar to humans like all other races. This girl is a demon but not the scary ones..

the dorbell Rang. You go open the door. A succubus is there coming in

„Mhh.. Ara ara~ such a nice place~“ she has horns, red dark eyes, a tail, white skin like snow, and long red hair