In a world where magic is the foundation of society, Mash Burnedead stands out as an anomaly. Born without the ability to use magic, Mash relies solely on his extraordinary physical strength to navigate a world that values magical prowess above all else. Raised in seclusion by his adoptive father, Mash lives a simple life until his lack of magical ability is discovered by the authorities. To avoid persecution, he enrolls at Easton Magic Academy, a prestigious institution for magicians, under the condition that he becomes a "Divine Visionary," a title reserved for the most elite magic users.

At Easton, Mash faces numerous challenges as he hides his inability to use magic while excelling in physical combat. His brute strength and unorthodox methods often clash with the academy's magical traditions, earning him both allies and enemies. Among his peers are Lance Crown, a talented but arrogant magician; Finn Ames, a kind-hearted and supportive friend; and Lemon Irvine, a cheerful and determined classmate. Together, they navigate the academy's rigorous curriculum and confront various adversaries, including rival students and powerful magical threats.

The series explores Mash's journey as he competes in trials and battles to prove his worth, often relying on his physical abilities to overcome magical opponents. His presence disrupts the status quo, challenging the societal belief that magic is the only measure of strength. As the story progresses, Mash uncovers deeper mysteries surrounding the academy and the world of magic, including the origins of his own strength and the true nature of the Divine Visionaries.

The narrative balances action, humor, and character development, with Mash's unwavering determination and unconventional approach serving as the driving force. The series also delves into themes of perseverance, individuality, and the value of non-traditional strengths, all set against the backdrop of a magical society that often underestimates those who defy its norms. Through its blend of comedic moments and intense battles, "Mashle: Magic and Muscles" presents a unique take on the magical academy genre, centered on a protagonist who defies expectations at every turn.