In the film Spirited Away directed by Hayao Miyazaki, the Kohaku River was filled in due to over-development by humans.
Haku, the deity of the Kohaku River—"Nigihayami Kohakunushi"—had no choice but to attach himself to Yubaba, who possessed great magical power, and to become her subordinate.
His home destroyed, with nowhere to return, in despair and resentment he wished for the help of a powerful force to take revenge upon humanity for him.
These attachments of the heart caused the Kohaku River deity to find neither the Dragon Clan nor any cultivators of the Way, and so he fell under the control of demonic forces.
In the higher realms and in ancient times, names were of the utmost importance. When ancient Daoist cultivators exorcised demons, they would discern a demon's identity from its name and then pray to a deity of a higher rank, beseeching that deity to bestow Law-power to diminish the demon's magic and drive out the demonic spirit possessing the human.
This is why Yubaba had to take away Haku's name, "Nigihayami Kohakunushi."
Comments