Youko

Youko is a female kitsune youkai whom Kantarou named. At the beginning of Tactics, Youko had already been living with Kantarou. She is loud and impulsive, and often loses her temper towards Kantaoru. Youko has the ability to make her fox ears appear and disappear at will, and can turn into her fox form if she wishes. Youko is shown to be deeply concerned about the household expenses and pesters Kantarou about finishing his book manuscripts. Before joining Kantarou, Youko was initially a lonely youkai who deceived travellers into thinking she was a member of their family. Youko pretends to be Kantarou's wife, but Kantarou soon reveals her to be a youkai, and invites her to join his household.

(Source: Wikipedia)