A young woman with mysterious origins discovers she has a gift for hunting demons and tries to save Gunn City.

Welcome to GUNN CITY, a fast-growing city where jobs are as easy to find as "gunnpowder" which enables people to work without getting tired. But Red, a young woman who grew up in the city's underworld, has just failed all her job interviews.
While trying to protect an artisan transformed into a monster by too much gunpowder, Red gets sent to the hospital, where she is healed with an experimental treatment. Soon, her soul will "awaken"... and she will become a demon huntress!