"I Can Not Be a Magical Girl" centers on the life of a young man named Yuuki, who unexpectedly finds himself thrust into the world of magical girls after a chance encounter with a mysterious creature. This creature, a small, otherworldly being, grants Yuuki the ability to transform into a magical girl, despite his gender. The transformation is involuntary and occurs whenever he is needed to fight against dark entities threatening the world. Yuuki struggles with the absurdity of his situation, as he must balance his ordinary life with his new responsibilities as a magical girl.

The narrative explores Yuuki's internal conflict and societal expectations, as he grapples with the embarrassment and challenges of being a male magical girl. His transformation not only alters his physical appearance but also forces him to confront stereotypes and prejudices. Along the way, Yuuki encounters other magical girls, each with their own unique abilities and personalities. These characters form an uneasy alliance with Yuuki, as they work together to combat the growing threat of the dark forces.

The story delves into themes of identity, self-acceptance, and the subversion of traditional gender roles. Yuuki's journey is marked by moments of humor, action, and introspection, as he learns to embrace his role and the responsibilities that come with it. The series balances lighthearted comedic elements with more serious undertones, creating a narrative that is both entertaining and thought-provoking. As the plot progresses, Yuuki and his allies uncover deeper mysteries about the origins of the dark entities and the true nature of their powers, leading to a climactic confrontation that tests their resolve and unity.