|Japanese Name||浅古 小糸|
- Eye colour: Unknown
- Hair colour: Purple
- Soul gem: Unknown, possibly the oval on her tie
- Weapon: Musket (?)
- Wish: Unknown
- Ability: Unknown
- Witch Form:
- Japanese pronoun: Watashi (私)
- Known relatives: Komaki Asako (older sister). Her parents have been mentioned but not seen
- School: Shirome Middle School
Koito is calmer and more friendly than her sister Komaki. She is seen displaying a lot of concern for the welfare of others and her sister.
Koito only appears in Sadness Prayer. After witnessing Komaki sneaking out various times at night, Koito begins to suspect she has a nightlife. Koito tried telling her parents, but Komaki dismissed it as stomach pains. Koito thus relays her suspicions to her friend Akira Namekata, who begins investigating into Komaki's supposed nightlife.
After her sister and Akira's deaths, Koito is overcome with guilt because she feels as though she should have stopped Komaki from going out. She also feels like Akira's death is her fault, as she is the one who asked Akira to watch Komaki. She talks with Oriko, who relieves some of her guilt.
At the very end of Sadness Prayer it's revealed that Koito made a contract with Kyubey and became a magical girl in order to help in the fight against Walpurgisnacht with Mami Tomoe, Kyoko Sakura and Yuma Chitose.
- Koito attends Shirome Middle School but she is not seen in the uniform until volume 3.
- Koito "小糸" means "small thread". This would fit thematically with her sister's name if translated as "small roll of cloth".
- Koito's last name, "浅古", means "shallow and old" or "superficially old".