Isaki Kudo is Chika Kudo's paternal aunt and sister to his father. After Gen Kudo's death, she offers Chika a place in her high-rise apartment, indicative of a likely high-paying job. She has shoulder-length black hair and is noted for her beauty, often emphasized by her attire.

Her personality is strong, independent, and blunt, with a quick temper mirroring Chika's. Her no-nonsense demeanor makes her difficult for him to oppose. Despite this rough exterior, she shows care through offering solid advice, her own method of concern. She occasionally embodies the "older sister" manga/anime trope, walking minimally clothed at home and giving Chika orders.

Isaki's dynamic with Chika is direct and physically expressive; she leaves belongings scattered and frequently hits him. The sleeping space she provides him is notably small, though it can be "expanded" at night. She actively involves herself in his personal life, encouraging a romantic connection between him and Satowa Hozuki, a fellow member of Tokise High's koto club.

Her connections include Suzuka Takinami, a math teacher and koto club advisor at Tokise High. They befriended during a cooking camp where Takinami assisted her, sharing a history as alumni of the same high school where Isaki was Takinami's junior (kouhai).

Her personal preferences include a liking for sake and a tendency to either sleep extensively or go out spending money on holidays. Residence in the expensive-looking apartment further underscores her probable affluent professional status.

Her given name combines "clothing, garment" (衣) and "blossom" (咲), while her surname Kudo signifies "long time" (久) and "distant, far" (遠).