Elaia, the daughter of an upper-class ``marquis'' in the country of Fendeliol, goes on a journey alone to escape her father's forced marriage and disappears.As the seasons change and time passes, Rust, a 17-year-old girl who lives as a ``professional mercenary'' who protects the country, appears in the local city of Fenderior.Numerous trials await Rust in the world of war, where men are proud of their skills.However, with her special skill "Seijutsu" and her outstanding action and nobility, Rust opens up a new life for her!Rust's journey, which begins in search of her own path in life, is soon confronted by a major battle over conflict between nations.The story of the growth and battlefield of a girl mercenary and her unique companions who later earned the nickname ``Whirlwind Rust'' begins here!! “Today, I would like to introduce myself as “Whirlwind Rust”! ”