"Broken Blade" is set in a fictional world where nations rely on quartz-powered mechs called Golems for warfare and daily tasks. The story centers on Rygart Arrow, a rare individual unable to manipulate quartz, making him an "Un-Sorcerer" in a society where this ability is commonplace. Despite his inability to pilot Golems, Rygart is drawn into a conflict when his homeland, the Kingdom of Krisna, is threatened by the neighboring nation of Athens.

The narrative begins with Athens launching a surprise attack on Krisna, exploiting advanced Golem technology that renders Krisna's defenses obsolete. Rygart, living a peaceful life as a farmer, is called upon by his childhood friends—King Hodr, Queen Sigyn, and General Baldr—to assist in the war effort. During an excavation, Rygart discovers an ancient, quartz-independent Golem named Delphine, which he can pilot due to its unique design. This discovery positions him as a key figure in the war, as Delphine's capabilities surpass those of conventional Golems.

As the conflict escalates, Rygart is forced to confront his own insecurities and the moral complexities of war. His relationships with Hodr, Sigyn, and Zess, a skilled Golem pilot and former comrade, are tested by shifting loyalties and personal sacrifices. The story explores themes of friendship, duty, and the human cost of warfare, as Rygart struggles to reconcile his desire for peace with the necessity of fighting to protect his homeland.

The series balances intense mech battles with character-driven drama, highlighting the emotional toll of war on both soldiers and civilians. Rygart's journey from an outsider to a pivotal figure in the conflict underscores the narrative's focus on resilience and the power of individual agency in the face of overwhelming odds. The interplay between political intrigue, technological advancements, and personal relationships creates a layered and engaging story that appeals to fans of both mecha and character-centric narratives.