Initially a reclusive girl, Kayoko struggled to go to school until she met Doremi, who was able to help her overcome it.
Kayoko is a very clever girl with an interest in reading and astronomy. She keeps to herself and is very shy and quiet, and she is emotionally fragile. However, she is also very nice and friendly.
She often experiences panic attacks at the thought of attending school to the point of becoming physically ill, and as a result she has a severe guilt complex.
Kayoko has fair skin and big, grey eyes. Her hair is maroon and cut extremely short. She wears an army green shirt with darker colored detail, khaki shorts with pockets, and a pair of shoes and socks matching her shirt. She has a meteor necklace she sometimes wears. Overall, she has a very boyish appearance.
Kayoko was often bullied and teased by her classmates in her old school and had to transfer to Misora Elementary as a result. Initially, the students of the class welcomed her with open arms; she became a close friend of Masato Rinno. But Kayoko proved to be a very slow worker with poor grades, and would often make the groups she worked with lose. Therefore, many students started rejecting her. When she asked Rinno for help, he couldn't comply due to a very busy schedule, and even told if she could "stop relying on him so much". This, along with the previous events and heavy pressure from the teachers and her own parents (especially her father as implied in one episode), caused her to withdraw herself from school.
She met Doremi Harukaze one day while vomiting into a bush out of anxiety. At first, she tried to avoid her as much as she could, until she realized how much Doremi was a friendly girl, and bonded with her and the Ojamajos.
Kayoko's repeated absence from school made both Seki-sensei and Yuki-sensei highly concerned; both would often visit Kayoko's parents. When Doremi learned about that, she started to help Kayoko getting over her fear of going to school, but also told her to take her time, as opposed to most adults who would put heavy pressure on her. Later, Kayoko revealed that she felt like a burden to everyone and wanted to disappear because of this, greatly implying suicidal thoughts. With the help of the Ojamajos, she eventually managed to go back to school, but at first could only stay at Yuki-sensei's cabinet.
She finally ended up revealing to Doremi and the whole class why she was afraid to go to school. Doremi gave her a hug and said she was a very nice person, causing her to break down crying into her arms. After Seki-sensei and Yuki-sensei talked to her parents about this, they decided to let Kayoko work at her own pace. On Christmas Day, with the support of all of her classmates and teachers, she stepped into the class.
Not much is known of what happened after these events, but it is implied that she became a very sociable girl. In the final episode of Dokkaan, she credits Doremi for allowing her to graduate with her friends.