Codename "Butterfly." In French, "papillon" means "butterfly," a name symbolizing Sally Yoshino, an intelligence agent of the National Intelligence Agency. She is assigned an extremely dangerous mission: infiltrate the underground organization "Servan," which plans to kidnap the agency's director. However, her actions are completely uncovered by Servan's leader, and she is gradually cornered. Captured, Butterfly refuses to surrender. Her strength and unwavering conviction drive the story forward with intense force.