Yayoi Honda is the younger daughter of Fumio Honda and sister of Sakura Honda, with their family owning and operating Honda Bookseller's—a bookstore once frequented by Kazuhito Harumi before his transformation. She possesses aubergine (dark purple-brown) hair and matching eyes. During an incident involving the bookstore's financial struggles and her father's disappearance, Yayoi captures Kazuhito in his dachshund form, then known as "Kuro." Frustrated by her family's situation and the store's potential closure, she involves him in her attempt to run away, entangling Kazuhito in her escape. Yayoi is credited with giving Kazuhito the nickname "Kuro" following his reincarnation as a dog. Her background is significantly defined by family relationships, particularly her bond with Sakura and their collective efforts to sustain the bookstore. The etymology of her name includes "Yayoi" meaning "all the more, increasingly" (弥) and "life, living" (生), while "Honda" translates to "root, origin, source" (本) and "field, rice paddy" (田).