The Sacred Blacksmith Seiken no Blacksmith

The knight Cecily wants to defend the weak, but her lack of skill makes her an unlikely heroine—until the blacksmith Luke comes to her aid, using magic to forge blades of supernatural strength. Cecily wields this sacred steel and charges forth to face a new threat; a cloaked fiend is unleashing demons upon the land, and though he lurks in shadows, the villain is closer than Cecily knows.

(Source: Crunchyroll)