Atsuko Kagari, known to nearly everyone as Akko, is a sixteen-year-old girl from Japan who serves as the main protagonist. Born into a non-magical family with no prior connection to witchcraft, her entire world changed when she witnessed a magic show by the celebrated performer Shiny Chariot as a young child. That experience left an overwhelming impression on her, and from that moment forward, she became determined to become a witch just like her idol, specifically to learn how to make people smile through magic.

Akko's personality is defined by her boundless enthusiasm, relentless optimism, and impulsive nature. She is an energetic and cheerful individual who tackles every challenge head-on, though her approach is rarely graceful or well-planned. Her impulsive tendencies often lead her into trouble, and she has a habit of acting first and considering the consequences much later, which frequently creates problems for herself and her friends. She can be stubborn, arrogant at times, and a little self-absorbed, but these flaws are tempered by a genuine and passionate heart. Akko is famously bad at standard magic, struggling with even basic spells and broom flight, a difficulty that is eventually revealed to stem from a magical incident in her childhood. Nevertheless, she possesses remarkable physical stamina and durability, surviving all manner of magical mishaps and physical trauma that would seriously injure most people. Her most defining trait is her status as a Determinator; she absolutely refuses to give up on her dreams no matter how many times she fails or how many people tell her she is not suited for magic.

In terms of her role in the story, Akko is a student at the prestigious Luna Nova Magical Academy. Because she comes from a non-magical background, she is looked down upon by many of her pure-blooded peers and much of the faculty, who view her as a talentless outsider. Her primary motivation is to follow in the footsteps of Shiny Chariot and become a witch who can bring joy to others. This quest is given tangible form when she discovers the Shiny Rod, Chariot's magical staff, which chooses her as its new wielder. The staff contains a powerful secret that requires her to unlock seven words, known as the Words of Arcturus, which are tied to specific magical feats and personal growth.

Akko's key relationships are central to her development. Her closest friends are her roommates, Lotte Jansson and Sucy Manbavaran. Lotte is a kind and sensible girl who often acts as Akko's voice of reason and offers quiet support, while Sucy is a cynical and mischievous mushroom enthusiast who frequently uses Akko as a test subject for her potions, though a deep, genuine friendship exists beneath the mockery. Her relationship with Diana Cavendish, the academy's top student, evolves significantly over the course of the series. Initially, Akko sees Diana as a cold, arrogant rival who dismisses her dreams, and Diana views Akko as a naive fool who does not respect the true traditions of magic. However, as they are forced to work together and witness each other's determination and compassion, their rivalry transforms into a deep mutual respect and a strong friendship. Her relationship with her teacher, Professor Ursula Callistis, is also incredibly important. Ursula serves as Akko's mentor, patiently guiding her and believing in her potential when no one else does. A significant part of Akko's journey involves the eventual revelation that Professor Ursula is actually her idol, Shiny Chariot, leading to a complex emotional reconciliation where Akko must come to terms with the fact that her hero is a flawed person who unintentionally caused her magical struggles.

Throughout the series, Akko undergoes substantial character development. She begins as a naive girl who dreams of becoming just like Chariot and believes in taking shortcuts to achieve greatness. An early lesson at the Fountain of Polaris teaches her that there are no shortcuts in magic; she must put in genuine effort and hard work to earn her accomplishments. Over time, her magical abilities improve, and she becomes particularly adept at transformation magic, a branch she initially found impossible. She learns that she cannot simply copy Chariot but must find her own path as a witch, leading to the realization that her unique strength lies in her unwavering believing heart. By the end of the story, she finally achieves the ability to fly on a broom, a basic skill that had eluded her throughout the series, symbolizing her growth from a complete novice into a true witch.

Akko's notable abilities, despite her initial struggles, are considerable by the end of her first year. She wields the Claiomh Solais, better known as the Shiny Rod, a powerful magical artifact that can transform into various forms, such as the Shiny Arc (a bow) and the Shiny Ax, each unlocked by learning a Word of Arcturus. Her signature phrase, and the core of her magical philosophy, is a believing heart is my magic. While this belief gives her spells a unique power born from pure emotion and determination, it is not just a catchphrase; it is the actual source of her strength, allowing her to perform miraculous feats when she truly believes in herself and her friends. She also demonstrates an incredible capacity for language learning, picking up complex magical languages like fish language in an astonishingly short amount of time. Her greatest feat is performed alongside Diana at the series' climax, where they combine their power to spread magic across the entire world, permanently altering its fate.