In the 23rd century, overpopulation on Earth pushed humanity to colonize space. Mars was first settled in 2050, but extremely high rates of stillbirth made long-term colonization impossible. The planet was converted into a prison colony in 2070 before being entirely abandoned in 2150. Some children born on Mars during this period developed genetic mutations granting them parapsychological powers, including telepathy, telekinesis, and teleportation. These abilities became more potent across subsequent generations. When humanity attempted to re-colonize Mars in 2264, they discovered the surviving Martian population and responded with attempts to exterminate and experiment upon them.

The story follows Sei Red, a proud fifth-generation Martian who possesses powerful ESP abilities. Forced into exile on Earth in 2276, she lives in New Tokyo City concealing her true identity as a white-haired, red-eyed extraterrestrial. One day, a mysterious boy named Erg discovers her secret. Claiming to also be connected to Mars, he invites her to return with him to the red planet, setting Sei on a fateful journey involving far more people than she ever imagined. As the narrative unfolds, Sei confronts the deep-seated discrimination and violent colonization that her people have endured.

The plot expands beyond a simple return home. Sei ultimately dies, but her consciousness survives in a liminal space. There she encounters various spirits with fluid sexual identities, which allows her to be reborn as a sixth-generation Martian. The story grapples with themes of colonization, scientific experimentation on marginalized populations, systemic discrimination, and cultural genocide. Sei's struggle represents a displaced person's longing for a lost homeland and culture erased by colonial powers. The series employs metaphysical concepts of death, rebirth, and consciousness as a commentary on identity and survival under oppressive forces. Star Red received the Seiun Award for Best Comic in 1980, recognizing its significant contribution to science fiction storytelling.