Luna Kozuki is a 15-year-old resistance fighter who battles the Android Army alongside her childhood friend, Tetsuya Azuma, who becomes the cybernetic hero Casshan. Her father, a scientist, created the essential Magnetic Field Gun, a weapon highly effective against robots. Luna plans and executes revolts within robot-controlled facilities and is entrusted with delivering weapon plans to the human resistance leadership. During one mission, her helicopter is shot down, and the pilot sacrifices himself so she can evade a robot scout team. She displays fierce loyalty, refusing to abandon Casshan even when he suffers physical weakness and urges her to flee. Luna also serves as a love interest to Casshan; after a difficult decision, she attempts to comfort him despite his initial rejection. She participates in the final battle where Casshan defeats the Black King, helping secure humanity's future.