Dr. Azuma's creation, the robot BK-1, is corrupted by a lightning strike and transforms into Braiking Boss, determined to subjugate humanity. To combat this new menace, Tetsuya, the doctor's son, undergoes a transformation into the formidable android Casshern. With his allies Luna and Friender, Casshern embarks on a mission to save his captured parents and thwart Braiking Boss's tyrannical ambitions.