"Sexy Magical Girl" centers on a young woman named Aya, who leads an ordinary life until she discovers she is the latest in a line of magical warriors tasked with protecting the world from supernatural threats. The narrative begins with Aya reluctantly accepting her role after encountering a mysterious talking creature, a mascot-like being named Mofu, who grants her magical powers. These powers come with a catch: her transformation into a magical girl is tied to her emotional state, often triggered by moments of intense vulnerability or passion, which adds a layer of unpredictability to her abilities.

The story unfolds as Aya battles a series of otherworldly entities known as Shadows, which feed on human negativity and manifest as grotesque, monstrous forms. Each Shadow is tied to a specific human host, often someone struggling with unresolved emotional turmoil. Aya’s battles are not just physical but also psychological, as she must confront the underlying issues of the hosts to truly defeat the Shadows. This dual focus on external combat and internal emotional resolution forms the core of the narrative.

Aya is joined by a small group of allies, each with their own unique magical abilities and personal struggles. These include Rei, a stoic and experienced magical girl who serves as a mentor figure, and Kenta, a non-magical but resourceful friend who provides tactical support. The dynamics between the characters are shaped by their shared mission and individual growth, with Aya often serving as the emotional anchor of the group. Her journey is marked by her gradual acceptance of her role and her growing confidence in her abilities, even as she grapples with the weight of her responsibilities.

The series balances episodic battles with an overarching plotline involving a powerful antagonist known as the Eclipse Queen, a former magical girl who succumbed to despair and now seeks to plunge the world into darkness. The Eclipse Queen’s backstory is revealed gradually, highlighting themes of loss, betrayal, and the corrupting influence of power. Her presence looms over the narrative, driving Aya and her allies to confront increasingly dangerous threats while also questioning the nature of their own powers and the sacrifices required to wield them.

As the story progresses, Aya’s relationships with her allies deepen, and she begins to uncover the true origins of the magical girl lineage. This exploration delves into the history of the Shadows, the role of the mascot creatures like Mofu, and the cyclical nature of the conflict between light and darkness. The series culminates in a climactic battle against the Eclipse Queen, where Aya must draw on all her strength, both magical and emotional, to save her world and redefine what it means to be a magical girl.