Kyoko is considered to be a very beautiful and cute girl with mid-back length chestnut-brown hair that she usually ties up into a bun or ponytail when dressing casually outside of school, golden eyes and a tall, slim figure.
Kyoko is most often seen donning her normal school uniform, which consists of a short-sleeved white shirt (long-sleeved in the winter), a red bow around her neck, a dark pleated skirt, black knee socks, and shoes. She occasionally wears her uniform vest, sweater, or blazer.
At home, Kyoko dresses in relatively casual and simple attire such as plain t-shirts and leggings or jeans. She keeps her hair tied up and at times, styled with hairpins. When cooking, she wears an apron.
Kyoko is normally a very energetic and popular person who always creates a happy atmosphere around herself. She is a hard-worker in all aspects of her life, and, according to Izumi Miyamura, she scores above 90% for all her tests. When nervous or embarrassed, she tends to switch to a violent state. This is seen when Kyosuke Hori asks if Miyamura was her boyfriend, resulting in her turning red and shoving a hot ladle into his face.
When she does ear cleaning, nail clipping, or massaging, she does it aggressively, which makes her feared by her family, her friends, and Miyamura. Miyamura has also mentioned in the chapter―that a q-tip looks like a weapon with a considerable offense when Hori wields it.
Hori is somewhat of a masochist- however this is only when it comes to Miyamura. Whenever he suddenly flips his personality to that of an abusive boyfriend for a short while (at her request), Hori enjoys the treatment and feels refreshed afterward. This is probably due to the fact that Miyamura is always calm and non-abusive.
She is also shown to be very jealous when girls are flirting with Miyamura to the point where Yuki Yoshikawa and Toru Ishikawa call her "Ice Queen". In some parts of the manga, she is also referred to as "Hannya" or the "Goddess of Jealousy". Over the course of the story, she does not seem to be too bothered with girls talking to Miyamura anymore but instead, worries that he might love a man. She once told him that it's okay to love another woman but not a man.
- The name Kyouko means "capital" (京) (kyou) and "child" (子) (ko).
- Kyouko's surname Hori means "moat" (堀).
- Hori stands at around 163cm, equal to about 5'4", and weighs 48kg (in Chapter 21: SOS, take note that the weighing scale says 41kg), which is the same as Izumi Miyamura.
- Hori does not wear any makeup when she's at home.
- Hori is terrible at tongue twisters compared to Miyamura, even though her grades are always better.
- Hori dislikes stew.
- Hori's favorite anime is Riho's World.
- Hori is both a sadist and a masochist as in Chapter 43 she appears to enjoy being shouted at by Miyamura, and also hit. (Also happens in Chapter 46 and Chapter 54).
- Hori won second place in the Horimiya character popularity contest on November 17th.
- On the webcomic ending, Izumi and Kyouko had a son named Kyouhei Miyamura.