"Make a pilgrimage for the past with me." It is these words, together with a haunting melody from her past, that draw professional assassin Mireille Bouquet into a partnership with Japanese schoolgirl Kirika Yumura, an amnesiac whose instinctive killing skills match Mireille's own abilities. Pursued by relentless and vigilant foes, Kirika and Mireille form a partnership code-named Noir, and begin a quest to discover the truths of their pasts, truths that could lead to their deaths.