Roze and Ash, undefeated mercenary brothers, face their greatest challenge when the "Neo Britannian Empire," occupy Japan. They join the Black Knights' Liberation Plan and resistance group "Seven Shining Stars" to counter the new invasion.

Roze and Ash, two brothers living in the old Hokkaido block of the United States of Japan in Year 7 of the Kowa Period, have become a formidable duo. Nicknamed the "Nameless Mercenaries," the pair are known to be undefeated in their operations, with Ash's advanced athleticism and Knightmare piloting skills and Roze's intelligence and strategizing skills. The brothers face their greatest challenge when Japan is occupied yet again by remnants of the Brittania Royalty calling themselves the "Neo Britannian Empire". To counter this new Britannian invasion, Roze and Ash accept a government request to assist the Black Knights' Liberation Plan and the resistance group known as the "Seven Shining Stars."