Chiyoko Kurotori, nicknamed "Choco" phonetically derived from her surname, is a fifth-grade student deeply fascinated by occult practices like black magic, curses, and horoscopes. A botched attempt to summon Cupid for love horoscopes—where nasal congestion mangled the incantation—accidentally conjured the black witch Gyubid instead. This forced Chiyoko into an apprenticeship under Gyubid, a role she undertook reluctantly and without inherent ambition. Despite her initial hesitation, Chiyoko revealed an unexpected knack for crafting mystical circles and casting spells. Her training mandated wearing a distinct loli gothic outfit during occult activities. She navigated supernatural mysteries throughout her apprenticeship while juggling ordinary school life.

Chiyoko progressed through the witch ranks, achieving fifth rank (marked by a red Jumber), then advancing to fourth and later third rank. Her dynamic with Gyubid shifted from adversarial to mutually respectful, with the trickster witch showing protectiveness, even sacrificing her own freedom using forbidden magic to save one of Chiyoko's classmates. Chiyoko's grandmother, Chikako Kurotori (real name Thika), secretly monitored her progress. Thika, possessing deep knowledge of the Spirit World, provided discreet aid and was later revealed as a former Black Witch Public Academy student expelled for breaking rules.

Chiyoko maintained her long-standing friendship with kindergarten companion Meg Shion, contended with rivals like Kyou Oogata (a former Angolmois student with sealed magic), and navigated unreciprocated romantic attention from classmates Ryoutarou and Taiyou, forming a love triangle. Her experiences required managing dual identities: an ordinary student by day and a witch apprentice during supernatural encounters, often leading to observations of her seemingly conversing with unseen entities.