This spirit is a guide to the underworld and Shiro Mujou's older brother.
His younger brother often needs to supervise him to make sure he gets things done.
Although often blunt and belligerent, he gets along well with his younger brother.
He loves Shiro Mujou and is prepared to sacrifice everything for him. Despite being ignored and rejected, he is not at all discouraged.
Surely that is just the way a big brother should be.