Kiichi is a fifteen-year-old girl who serves as a fighter for the First Ship of the defense organization known as Circus. She is of short stature with wavy, dark blue or blueish-purple hair that is typically kept in a bob cut and curls slightly at the ends; her eyes are the same shade as her hair. Kiichi has a refined sense of fashion and often has a composed and put-together appearance.

Kiichi possesses a strong-willed and proud personality, identifying as a perfectionist who holds herself and others to high standards. She has a deep-seated hatred for losing and is highly competitive, which serves her well in battle. She typically deals with situations in a calm and logical manner, often choosing the success of a mission over sentimentality or concern for fallen comrades. This blunt and logic-driven approach can make her seem harsh or self-serving, as she is not afraid to speak her mind directly. Kiichi has a particular disdain for the members of the Second Ship, frequently calling them useless and taking pride in her own vessel and rank. She enjoys provoking the proud Gareki, ordering him around and daring him to complete tasks she believes he cannot, which often leads to conflict between their equally prideful natures. Despite her often abrasive exterior, she does show a capacity for kindness, particularly towards younger or more vulnerable individuals, and becomes more protective as she grows closer to them.

Kiichi's primary motivation stems from her pride in her abilities and her position within Circus. She is driven to complete her missions perfectly and to prove her competence, holding a particular desire to avoid being looked down upon or seen as inferior. This competitive drive fuels her one-sided rivalry with Tsukumo, who was her senior by one year at the Kuronomei Academy and towards whom Kiichi feels a need to prove herself. The rivalry is not mutual, as Tsukumo is largely unemotional and unconcerned with competition. Kiichi also holds a competitive view of Yogi, who holds the same rank as her, and she is quick to lecture him when he fails. Her relationships with other Circus members are more nuanced; she works alongside Jiki and engages in good-natured teasing with him. While she initially dismisses Nai as unworthy of notice, she eventually grows close to him and shows him genuine kindness, even becoming defensive when his well-being is questioned.

In her role within the story, Kiichi acts as a skilled and competent fighter for the First Ship, often participating in dangerous missions. Her development is seen through her interactions with the core group, particularly her shift from outright dismissal of Nai to a caring, almost protective figure in his life. Her rigid and logical approach to mission parameters also softens slightly as she forms these personal bonds.

Kiichi possesses notable abilities that make her a formidable fighter. Like most members of Circus, she has the ability to fly at certain speeds. Her primary weapon is a large scythe, which she wields with high proficiency despite its size. Her specific ability, referred to as severance, allows her to cut away parts of a person that have been infected by a special power, and she can also stop the bleeding from that wound for a period of ten minutes.