The story follows Rust, a master-rank alchemist who heads the basic research department at the Alchemy Association in the royal capital. His department is responsible for creating the high-quality foundational materials essential for the association's products and other alchemists' work. Despite his expertise, the association's president, a former bureaucrat, fails to understand the importance of basic research. Rust is given menial tasks preparing materials for other departments, and his budget is repeatedly cut. When he is informed that next term's budget will be reduced to zero and his department will be disbanded, orchestrated in part by a colleague named Riharuzamu, Rust decides to leave. On the same day, he receives an invitation from an old school friend, Karin Admiral, a former knight who has been granted a frontier territory for her achievements in war. Seeing no future at the association, Rust accepts her offer and resigns.

Rust is a calm and pragmatic young man who wields tremendous alchemical skill, capable of transmuting materials of a quality that cannot be found elsewhere. He also commands a chimera-like transmuted beast named Rose, which assists him in his work. Karin Admiral is a cheerful and friendly woman who possesses superhuman strength inherited from giant lineage, making her a formidable warrior. However, she struggles with administrative duties and is haunted by nightmares of subordinates lost in the war. Her domain is staffed by loyal warriors, including the Saad sisters. Ari Saad wields a future-seeing evil eye that she conceals behind a face covering, while her sister Roa Saad is equally skilled. The frontier territory itself is a harsh, undeveloped land facing numerous challenges, including an endemic disease that has afflicted many of Karin's people.

The early narrative follows Rust's departure from the association, which quickly descends into chaos as his irreplaceable contributions vanish. Upon arriving at the Admiral Domain, Rust is immediately tasked with solving the mysterious paralytic disease plaguing the populace. Using a mobile tent and customized potions, he efficiently treats all affected patients in a single day. He then investigates the cause, discovering the illness stems from excessive magic elements in the soil. His solution involves creating a device to purify the land, effectively resolving the crisis. A major early arc involves Rust encountering a traveling priestess named Taura, a survivor of a religious order destroyed by a mysterious sorcerer. Cursed and dying from poison, Rust heals her with a custom potion, inadvertently breaking her curse as a side effect. In return, she swears to become his sword should he ever face disaster.

Later arcs involve Rust taking on various development projects to improve the frontier, from road construction to establishing trade in magical crystals. He also confronts threats such as giant mole-like monsters and aerial enemies. Throughout these events, his former employer begins to feel the immense consequences of his departure, with Riharuzamu attempting to manage the fallout he helped create. As Rust continues his work, he earns the respect of Karin's household and steadily transforms the struggling border domain into a thriving territory, while the Alchemy Association that dismissed him finds itself in an ever-deepening crisis without its most talented alchemist.