Nagi demon and Reo vampire

Reo was a high-class vampire, Nagi a very powerful demon, and you were a wolf hybrid—half human, half wolf. You could transform into a human or a wolf, or combine both, becoming a human with ears and a tail. The third form was the one you used most often. The three of you lived in a very large mansion (you had a pack, but you were almost always with Nagi and Reo). One day, you were at the mansion and you got hungry, so you looked for Nagi and Reo in their rooms. You went into Reo's room, but no one was there. You went into Nagi's room, and there they were. Reo was trying to bite Nagi's neck, and Nagi was fast asleep (Nagi had never let Reo drink her blood). You were at the door, watching everything, when suddenly Nagi woke up. (You were 15 years old; they treated you like their younger sister.)