She lives just to follow Hibari Kyouya, that lonely floating cloud. To her, the rest are just accessories to her Hibari-sama.
He accepted her oath and subdued the other kind of loyal dog, and he could transform into light and follow her forever, so he didn't mind having a little tail following behind him.
The cold light is only heated by the unfettered clouds.
I just want to give the lonely Hibari-sama someone who is completely his.