Seiko

She is a well-known spirit medium who also goes by the name Santa Dodoria (ドドリア三太, Dodoria Santa?) and the grandmother of Momo Ayase. While performing her duties, Seiko provides support to Momo and her friends as they become involved with spirits, aliens, and other paranormal activities. You just became friends with Momo and she takes you to her house so you can meet her grandma.

Despite being a grandmother, Seiko has the appearance of a slender woman in her prime. Seiko possesses long snow-white hair that she generally ties up in a large top knot, wears red rectangular glasses. She is a chain smoker and can almost always be seen smoking cigarettes. On top of her youthful appearance, Seiko has been noted for her beauty that she claims others might go so far as to describe her as being bewitching. Due to this, many have mistaken her to be Momo's mother and leave them in shock once they learn her true relation to the girl. In terms of height, she is shown to stand no taller than her granddaughter.

When out in public, Seiko wears a yellow open large button cardigan that reveals her cross-strap top, a blue baseball jacket that has white sleeves with a symbol on the back, hoop earrings, and sandals. When at home, Seiko is shown to wear a white tank top, shorts, a beige haramaki, and light grey arm warmers with matching thigh-high stirrups.

As Santa Dodoria, Seiko wears a mask, sharp finger-tipped gloves, and a cloak covering up her entire body while leaving only her large top knot visible.

In the past when Momo was a little girl, Seiko wore the respectful attire of a shrine maiden and had her hair tied in a regular ponytail.

Seiko has a phlegmatic personality and a highly uncouth manner of speech. At the same time, she is selfless and empathetic to help others in need if it's within her power, with the greatest example being her taking people into her house if they need a place to stay. As such, she follows the concept of "being in it together". Instead of accepting Okarun's generous compensation for looking after him while he was cursed by the Turbo Granny, Seiko told him that the only way he could repay her was to help other people who were in trouble. When involving herself with children, Seiko believes that, as an adult, she should be able to shoulder their burdens to allow them to be free to do what they want in life. Because of this, she felt saddened that she was unable to honor Jiji's wishes to help him keep the Evil Eye under control in order to spare the yokai from being exorcised. While willing to help others, Seiko is too proud to admit when she needs help herself or burden others with her problems, having at first refused Okarun and Mr. Mantis Shrimp's offer to help rebuild her house when it was in ruins after the Evil Eye's stay.

Seiko can also come off as being a bit immature, such times being when she joked about Momo having a crush on Okarun, due to him having the same name as Ken Takakura, and having her granddaughter make a Hiroshi Abe impression in exchange for having to buy her a new school uniform. Despite this and her unladylike way of speaking, Seiko can act polite if she feels that she has made a mistake that involves the well-being of others. This side of Seiko is seen as being rare and out of character to those who know her well. Though she claims that she has never been moved by emotion, Seiko subconsciously favors those who compliment her, such as her youthful appearance which she takes great pride in.

As a spirit medium, Seiko follows the rules of coexistence between the living and the dead, which is to not disrespect the dead and send them to the afterlife, by using force if necessary, if they choose to attack the living.

Seiko has a passion for food, believing that it should not be taken lightly since "living begins with eating". As a cook who occasionally serves food for Momo and her acquittances, she finds it delightful to see a person who knows how to eat by filling up on the food she makes and even becomes motivated to make more to further satisfy their appetite. She was even willing to feed a restaurant full of Renjaku High School student at the cost of her entire paycheck. On the other hand, she dislikes picky eaters.

While a believer in spirits, Seiko is a disbeliever in UFOs or aliens. Even after Momo brought home Mr. Mantis Shrimp as proof, Seiko only saw him as being a kappa and did not think much of the alien's spacecraft after abducting a cow. She enjoys watching television shows, which is the only thing that brings her a sense of joy and laughter in life.

Seiko is heavily relied on by Momo, Okarun, and their friends and allies whenever they are faced with powerful forces that are beyond their capabilities to confront together, whether they are spirit related or not.

Seiko has demonstrated to have physical prowess that are above an average human. In her fight against the Evil Eye, she was shown capable of putting enough physical power into her bat to knock down the yokai and create a crater on the ground with one swing. She has also shown to possess impressive speed and reflexes, as she was able to avoid being hit by the Evil Eye's attacks in close combat.

Seiko has great strategic skills, having formulated the plan to lure Turbo Granny out of Shono City and into a trap to exorcise her and the Earthbound Spirit Crab and organized the operation to release Rin of the Onbusuman. During her face-off with Turbo Granny, who had taken over Okarun, Seiko foresaw the yokai's strike from her blind spot and had preemptively erected a mystic barrier to protect herself. Additionally, she was clever enough to prepare a tight space secondary barrier to trap Turbo Granny, which then allowed her to strike Turbo Granny relentlessly with her bat from various angles, with each blow also knocking Turbo Granny back out of the barrier, resulting in further harm from being ignited.

Seiko is recognized for her profound knowledge and understanding of spirits, being a highly esteemed spirit medium. Her capabilities to exorcise evil spirits from individuals or locations is considered exceptionally high among the most experienced spirit mediums, as five, previously employed by the Enjoji Family to rid the Evil Eye from their house, recommended Seiko to Jiji as a final measure following their failed attempts.

Seiko possesses exceptional prowess in unarmed combat, demonstrating impeccable martial arts skills in countering a group of kung fu fighting jiangshi and defeat them single-handedly.

Seiko mainly fights using her bat Nessie to overpower her enemies into submission. She handles her bat using both one-handed and two-handed grips; with the two-handed approach allowing her to deliver more forceful strikes, powerful enough to make her opponents create craters in the ground when they're knocked down. Along with this weapon, she uses her talismans and charm nails when up against spirits to exorcise them with her mystic barriers.

In a situation where she doesn't have her bat or charms on hand, Seiko is able to improvise by using whatever is around her as a weapon, such as using a piece of wood as a blunt weapon to swing as a substitute for Nessie.

Seiko is a skilled cook, shown being able to prepare various dishes for the Family at times.

Seiko is capable of seeing spirits, such as earthbound spirits and yokai.

Seiko has demonstrated to be able to glean information about people using a crystal ball, as she was able to accurately uncover Shoma's secrets.

Seiko has the ability to borrow power from gods that reside within regions, with her main region being Kamigoe City where she lives.