Roze

She is one of Cerberus head and was the cause of giving Chiaki the curse because she was frightened at that time when she was mistreated by humans.

She seems to be the healer of the three heads, but other than that it's unknown.

She was sent to Chiaki to be his guard dog by Chiaki's father. She also wears a muzzle to atone for Chiaki's Curse.

She appears when you pull Cerberus tail.

(Source: AkatsukiUlquiora, edited)