In the dark century, the devil Vandel tyrannizes over the people and manipulates monsters. The Vandel Busters seek out and defeat these devils, and the strongest among them are the Zenon Squad. Beet, a young boy with a dream of joining the Squad, causes their defeat at the hands of Beltose. As the Squad dies, they give their powers to their weapons, known as Saiga, and bestow them upon Beet. Years later, Beet sets out on a mission to fulfill the Zenon Squad's mission and put an end to the dark century.