Nayuta, a high school girl, intervenes when she encounters a distressed woman and her mysterious son, Kiro. After escorting the woman to a hospital, both vanish without a trace, with staff denying Nayuta ever brought them. Kiro later materializes in her room, demonstrating telepathy and identifying himself as an esper. His tiara unexpectedly awakens Nayuta's latent esper abilities. Once she possesses the tiara, she gains the power to detect green-skinned aliens camouflaged among humans. This revelation draws her into a resistance movement combating these extraterrestrial observers secretly monitoring Earth.

Nayuta's involvement intensifies over time, culminating in a journey to Pluto where she uncovers the true nature of the universe and humanity's role within it. These complex cosmic truths clarify the aliens' motives but prove initially bewildering.

Initially, Nayuta displays traits typical of shoujo manga protagonists: helplessness, stubbornness, and bouts of frustration while adapting to her powers. By the story's second half, she evolves into a proactive, resilient figure confronting alien threats. Her relationship with Kiro deepens meaningfully through shared trials, paralleling his own significant character development later in their mission. Key allies include Soz, the resistance leader noted for a unique costume, and fellow fighters opposing the alien presence, with Nayuta central to their efforts. Visually, the narrative reflects 1980s anime aesthetics through simpler character designs and occasional animation inconsistencies in action scenes, while costumes for pivotal characters like Soz and Kiro feature greater elaboration and distinctiveness.