Chihiro, what a pretty name. You take good care of it.
- —Zeniba to Chihiro
Because she is Yubaba's twin, Zeniba's appearance is identical to that of her sister's: an inhumanly-large head with long, white hair tied up into a bun, a wrinkled face consisting of a large, hooked nose, a red dot in-between her eyes, and she wears blue eye-shadow, large golden earrings, and a dark blue dress set with a ruby brooch at the collar. The only distinguishing feature between the sisters is that Zeniba is shown to wear glasses, implying she may be far-sighted, as evidenced by the fact that she only wears them when weaving in her cottage.
When she first appears in the second half of the film, she seems to be just as dangerous as her sister is. After wreaking havoc in Yubaba's office, she warns Chihiro Ogino to keep quiet about the incident or she will rip her mouth out. When Chihiro refuses to hand over Haku and the golden seal, she becomes angry and yells at Chihiro, informing her that Haku is a greedy thief who needs to be punished, and that she placed a curse on the golden seal so that whoever steals it will die. She also appears to particularly dislike her nephew, Boh, shown when she makes fun of his weight and low intelligence.
When Chihiro visits her cottage in Swamp Bottom with No-Face, Boh and Yubaba's Bird in order to return the golden seal and apologize on Haku's behalf, her true nature is revealed as a kind and helpful old lady. She gives encouraging advice to Chihiro about remembering Haku's name and later forgives Haku for the theft of her seal. She appears to form a bond with Chihiro, seen when Chihiro refers to Zeniba as "Granny" at her request.
Zeniba first appears in the second half of the film. When Chihiro sees Haku in his dragon form being chased by the paper spirits conjured by Zeniba, she sees him crash into Yubaba's penthouse. Upon rushing there, one of the paper spirits follows Chihiro and attaches itself to her back. When she finally finds Haku in the office, being pushed down the chute by the Three Heads, she manages to stop them just as Boh crashes through the room in pursuit of Chihiro. When he begins to cry, Zeniba finally reveals herself when the paper spirit detaches itself from Sen and conjures up a transparent apparition of her. Taking delight in the circumstances, she wreaks havoc, transforming Boh into a small mouse, Yubaba's Bird into a tiny crow, and the Three Heads into a mimic of Boh's original form.
Zeniba lets Chihiro go as a thanks for leading her to a dying Haku, but threatens to rip her mouth out if she tells anyone about what she has witnessed. She demands Chihiro to move away so she can deal with Haku, but Chihiro refuses, stating that Haku is a good person. Zeniba then goes on to explain that Haku stole her powerful magic seal, and that he is a corrupt being who only became Yubaba's apprentice so he could steal her magic, and then goes on to state that Haku is dying because of a curse on the seal anyway. Whilst the Three Heads, now transformed into a Boh mimic, begin to bang around, Zeniba is annoyed and turns around to deal with them, giving an almost-dead Haku a chance to smash the paper spirit projecting her image, resulting in her apparition being sliced in half (apparently doing no actual harm to Zeniba herself).
Later on, despite warnings from Kamaji, Chihiro decides to take the seal back to Zeniba and apologize for Haku's actions. After taking the spirit train to Swamp Bottom, a magical Hopping Lantern leads Chihiro and her three followers (transformed Yu-Bird and Boh and No-Face) to Zeniba's cottage, where she greets them warmly. She subsequently invites them inside for tea. When Chihiro gives her the seal and says that she squashed a little black slug, Zeniba laughs and claims that she accidentally destroyed a parasite that was put into Haku by Yubaba to control him, and that her own curse from the golden seal was broken by Chihiro, whose love for Haku had proven to be more powerful. She gives Chihiro advice on remembering Haku's name so he can be free, and then compliments No-Face on his excellent weaving when she gathers everyone for a sewing session. When it is time to leave, Chihiro thanks Zeniba for all she has done, and entrusts Zeniba with the secret of her true name. Zeniba remarks that it is a beautiful name, then turns to No-Face and offers for him to become her apprentice in weaving, to which No-Face happily accepts. When Haku arrives to take Chihiro back to The Bathhouse, Zeniba personally forgives him. She is last seen waving with No-Face to Chihiro, who waves back whilst riding on Haku into the sky.
Zeniba is an extremely powerful witch whose magic could easily rival that of her younger twin sister, Yubaba. Kamaji also once commented that she was "one dangerous witch". Examples of powers she was shown to possess were:
- Magic: Zeniba is formidably skilled in manipulating supernatural energy that enabled her to alter the fabric of reality and defy the laws of nature. Even Haku, who was a powerful spirit in his own right, was no match for her magic, and were it not for Chihiro's and Kamaji's timely assistance, he would have been killed. Examples of abilities Zeniba derived from her magic are:
- Paper Charms Magic: Zeniba had the ability to create magical paper charms or talismans to serve a multitude of purposes - she conjured a large flock of manikin-shaped paper shikigami to pursue and offensively attack Haku after he had stolen her seal, and later on she astral-projected herself into Yubaba's office through possessing one of the shikigami.
- Spirit Possession: Zeniba had the ability to possess the essence of spirits or other supernatural entities, as demonstrated by how she possessed one of the paper shikigami to guide Chihiro to find Haku.
- Astral-Projection: Zeniba had the ability to project her consciousness into a transparent astral-form outside her body.
- Transformation: Zeniba had the ability to manipulate reality to transform any object or being into something else, which she channeled through her hands - with mere hand gestures, she transformed Boh into a small mouse, Yubaba's Bird into a tiny crow, and the Three Heads into a mimic of Boh's original form. It is possible that she possessed this ability to a highly advanced degree, for not even Yubaba (a formidable witch herself) was able to see through the transformations initially, and only realised it when Haku hinted it to her.
- Telekinesis: Zeniba had the ability to move objects as well as individuals with her mind, which she like her sister Yubaba channeled through her hands. She closed her front door without physically touching it when Chihiro came to visit her.
- Cursing: Zeniba had the ability to cast magical enchantments or spells designed to cause negative effects to occur - during her and Chihiro's first meeting, she revealed that she had placed a dying curse on the seal that Haku stole, and it was subsequently confirmed by Kamaji, who observed that Haku was dying due to the cursed seal he swallowed, for it caused him to bleed from the inside. It is also possible that Zeniba possessed this ability to a highly advanced degree, given how Kamaji described it as "strong magic", and she herself later explained to Chihiro that only true love could break her curse.
- Sensing: Zeniba had the ability to determine the location and status of other beings by concentrating on them, as shown by how her hopping lantern guided Chihiro and her companions to her cottage, and when she opened the door for them, she revealed that she had long been expecting them.
- Arcane Knowledge: Zeniba possessed an extensive knowledge of magic and the spirit world, as demonstrated by her conversations with Chihiro during their second and final meeting.
- "There now, your body now matches your brain."
- "Zeniba. I'm Yubaba's twin sister."
- "Ouch! A paper cut."
- "He sliced me in two, you know, and I'm still angry."
- "We're identical twins, yet exact opposites."
- "Do you know why he became my sister's apprentice?"
- "He's a greedy little thief; there's nothing good about him."
- "Squashed it?"
- "You squashed it!"
- "The spell on those two wore off long ago; turn back if you want."
- "No-Face, why don't you stay with me?"
- "That's love for you."
- "To steal her magical secrets, and now he's stolen my magic, too."
- Kamaji once referred to her as "one dangerous witch".
- Zeniba is the second of two witches seen in the film. Yubaba was the first witch.
- Yubaba used Haku to try and steal her sister's magical secrets from her.
- Zeniba owns a solid gold monogram seal.