Kushimatsu is a full-blooded fox spirit possessing a head reminiscent of a cartoonish weasel, covered in pure white fur. Her eyes remain characteristically closed in her typical form. She wears a traditional light purple kimono and stands approximately at human height. She possesses an alternate form, manifesting as a significantly larger, more elegant fox, comparable to a horse or exceeding it in size depending on the situation; in this state, her eyes open to reveal bright green irises framed by long, dark lashes.

Her background includes prior service to Tsukuhane, Zakuro's mother, before Tsukuhane's disappearance. Following this event, Kushimatsu assumed responsibility for raising Zakuro for the majority of her life. She also orchestrated the relocation of Bonbori, Hozuki, Susukihotaru, and Zakuro from their disparate regions to live together under her care. Operating within the Ministry of Spirit Affairs, Kushimatsu receives cases from those seeking aid and assigns missions to the group she oversees.

Her relationship with Zakuro is generally amicable, though occasional friction surfaces when Kushimatsu excludes Zakuro from certain missions, prompting Zakuro to question these decisions. This reflects her dual role as both caretaker and mission coordinator.

Her name, "Kushimatsu," combines the Japanese words "kushi" (櫛), meaning "comb," and "matsu" (松), meaning "pine tree" or "fir tree".