Youko

Encyclopedia Entry:

Strong human-like monsters with the characteristics of a fox.  They live in forests or mountains, luring their targeted, unsuspecting male visitors into their den to be seduced, most then getting engaged with their victim and eventually moving into a human village with him.  The number of their tails is a measuring stick for how powerful their magic is, in addition to how lustful they are.  The maximum number of tails a youko can have us nine.