Ageha, known as the Butterfly Girl, is one of the three central protagonists in the 1973 science-fiction action series. Her name is the Japanese word for swallowtail butterfly, which directly informs her visual design and thematic role. She is a young humanoid female with short, cropped hair that is typically hidden beneath her cyborg helmet. Her most defining feature is the pair of colorful, bright yellow wings attached to her back, which are modeled after the Asian Swallowtail butterfly species. These wings allow her to take flight, a core ability she uses in her mission.

Ageha belongs to a group of beings known as microids, which are classified as intermediate creatures between insects and humans. While sharing a common ancestor with humanity, microids have been miniaturized to a tiny size and developed under the care of insects. Ageha, along with her companions Yanma and Mamezo, was enslaved by the Gidron, a highly advanced empire of intelligent ants living in a vast underground complex in the Arizona Desert. The Gidron seek to purge the Earth of pollution-causing humans, and they use the microids as a labor force. Ageha managed to escape from the Gidron nest alongside Yanma and Mamezo, making the journey to Japan. Their primary goal is to warn humanity of the imminent danger posed by the Gidron and their plan to conquer the human world.

In terms of personality, Ageha embodies a mix of maternal warmth and feisty warrior spirit. She is depicted as brave, determined, and resourceful, often placing the safety and well-being of others before her own. Her role within the trio is largely supportive; she acts as a steady and calming presence, frequently watching over the trouble-prone Mamezo and pulling him out of harm's way. Despite her nurturing demeanor, she is no passive character. When the situation calls for it, Ageha demonstrates a fierce combat ability and a willingness to fight, using her helmet and built-in technology to defend herself and her allies. She is not merely a damsel in distress but an active participant in the battle against the Gidron.

Ageha’s primary relationships are with her two fellow escapees. She works closely with Yanma, the dragonfly-themed leader of the group who is the primary fighter and often uses a Microid Beam from his helmet to destroy enemy robots. While Yanma takes the lead in direct confrontation, Ageha provides crucial backup and support. Her other key bond is with the young Mamezo, the beetle boy of the group. Ageha frequently acts as a protective, almost motherly figure towards him, ensuring he stays safe during their many dangerous encounters. Together, the trio eventually meets Dr. Midoro, a Nobel Prize-winning scientist, and his son Manabu. The doctor becomes one of the few humans who believes their warnings and offers them assistance in their ongoing struggle.

Development for Ageha is tied to the overarching plot of the series. She begins as an escaped slave and, over the course of the story, fully embraces her role as a defender of humanity against the insect empire. Her tragic backstory, which includes losing her parents to robot attacks in her youth, serves as the foundational motivation that drives her desire to protect others and fight against the threats posed by the Gidron. This past trauma hardens her resolve and explains her deep commitment to the cause, transforming her from a survivor into a dedicated warrior. Her notable abilities include powered flight using her butterfly wings, proficiency in hand-to-hand combat, and the operation of the technological systems built into her microid helmet and suit, which are standard for her kind.