Coco is the central protagonist of the story, a young girl whose life is transformed by a single, irreversible mistake born of pure wonder. Before becoming a witch's apprentice, she lived an ordinary life working as an assistant in her mother's dressmaking shop. Her greatest dream was to become a witch, a status she believed was impossible because she assumed magical ability was something a person had to be born with. This fascination began in her childhood when she attended a castle fair and received a mysterious magic picture book from a masked witch, an encounter that sowed the seeds of her lifelong obsession.

Coco has a bright blonde or yellow-green bob and golden eyes, and she is often described as having an endlessly cheerful and optimistic demeanor. Her most defining trait is a deep, childlike enthusiasm for magic; she looks at even the most common spells with wide-eyed wonder. This inquisitiveness makes her an ideal protagonist, as her constant questions about how magic functions naturally explain the world's rules to the reader without feeling forced. While she is kind, energetic, and eager to help, she can also be clumsy and sometimes hides her anxieties behind a smile, shouldering a heavy emotional burden quietly.

The tragic event that alters her path occurs when she secretly uses an old magic book to cast a spell. She witnesses the witch Qifrey performing magic and learns the secret of the craft, which involves drawing precise glyphs with special ink. In her excitement, she draws a forbidden spell, which accidentally turns her mother into solid stone. Qifrey finds her and is obligated by the rules of the magical assembly to erase her memory of the incident. Coco refuses desperately, and due to her connection to the masked witch who gave her the book, Qifrey instead takes her on as his personal apprentice. Her primary motivation becomes twofold: to fulfill her lifelong dream of mastering magic and to find a way to reverse the spell and save her mother.

Within the group of apprentices, Coco is unique. She is the only one who grew up outside the magical world, and her lack of formal training makes her clumsy and prone to mistakes compared to her peers. However, her background as a dressmaker gives her an unusual advantage: she is exceptionally skilled at drawing straight lines and conceptualizing shapes, a skill that proves vital in spellcasting. Her inexperience also grants her a creative freedom that trained witches lack. While others strictly follow established forms, Coco invents practical, makeshift solutions, such as turning a boat sail and cloak into a flying device to pass a dangerous test.

Coco has a complex relationship with her fellow apprentice, Agott. Initially, Agott despises Coco, viewing her as an outsider who cheated her way into the atelier without earning her place. In an attempt to get rid of her, Agott forces Coco to take a dangerous trial for which she is unprepared. Yet, during this trial and subsequent life-threatening adventures involving dragons and forbidden labyrinths, Coco proves her perseverance and strategic thinking. Over time, Coco's sincerity and talent for "ideas" earn Agott's respect, slowly transforming their rivalry into a close friendship.

Her relationship with her mentor, Qifrey, is deeply layered. While he genuinely cares for and teaches her, he is also secretly using her as a lead to track down the Brimmed Caps, the rogue witches who use forbidden magic and are responsible for the spell that turned her mother to stone. Coco is initially unaware of this hidden agenda, making her an unwitting piece in a larger, dangerous conflict between magic factions.

Throughout her journey, Coco undergoes significant development that challenges her initial naivety. After an accident where a boy named Custas loses the use of his legs, he later turns to forbidden magic for a cure when conventional spells cannot help him. This encounter forces Coco to confront the darkness of the magical world head-on, teaching her that even magic that seems helpful can be forbidden for very serious reasons. She learns that magic is not just beautiful and wondrous, but carries enormous consequences, a lesson she carries with her as she grows from a starry-eyed fan into a responsible witch-in-training.

In terms of abilities, Coco is a beginner who knows only basic spells for daily tasks like creating wind, fire, or pulverizing objects. Her true talent lies in her creativity and her knack for combining simple shapes and concepts to solve complex problems. She struggles with technical finesse, but her bravery borders on stubbornness; she never gives up, even when facing immense danger or failure, picking herself up to try again with the same infectious smile.