 One belief is that when a kitsune changes shape , its hoshi no tama holds a portion of its magical power . Another tradition is that the <unk> represents the kitsune 's soul ; the kitsune will die if separated from it for long . Those who obtain the ball may be able to extract a promise from the kitsune to help them in exchange for its return . For example , a 12th @-@ century tale describes a man using a fox 's hoshi no tama to secure a favor : 
