Space detective Diana has been captured by the Garar Empire's secret base and is subjected to brutal torture. However, her comrade Lukeban arrives unexpectedly to rescue her, allowing her to narrowly escape. During the ordeal, the enemy discovers a critical weakness in Diana's transformation system. Later, while investigating alone again, Diana encounters a new Weapon Monster and is ambushed during her transformation, captured once more. This time, the enemy's leader, Emperor Gillron, is captivated by Diana's beauty and calm demeanor, suddenly proposing marriage. Diana firmly rejects him, but the Emperor, increasingly obsessed with her youthful and alluring appearance, begins forcing an intimate relationship upon her.