It is the year 2046, Noboru Terao and Mikako Nagamine are close friends who will soon be graduating junior high school. But after an alien attack on humanity, Mikako is selected for the UN military space expedition set to retaliate against the aliens. Separated, Noboru and Mikako attempt to keep in touch by sending emails to each other with their cell phones. Yet as the expedition journeys farther from Earth, the time it takes for them to transmit and receive each other's messages increases substantially. Hoshi no Koe revolves around the relationship between this couple as they try to stay connected despite the growing distance between them. [Written by MAL Rewrite]

Tsubasa Shiina is a 10-year-old girl who recently moved to Hokkaido to live with her father. In school, she is very quiet and unsociable with her classmates. Then one night, she witnesses a UFO crash in the forest near her home. She rushes to the scene and finds the pilot, codenamed "D.D.", in a barely stable condition. Also in the scene is a Maguar, a hideous alien that hatched aboard D.D.'s ship. As the Maguar is close to taking Tsubasa's life, an alien lifeform fuses with her body to form the Riberus battle armor Figure 17, which shortly destroys the alien threat. The life form takes the name Hikaru and turns into an identical twin of Tsubasa. As time passes, Tsubasa becomes more open to everyone around her, thanks to her new twin sister Hikaru. However, with Maguar eggs scattered all over Hokkaido, their ability to form Figure 17 is needed to eliminate all hatched Maguars until backup from D.D.'s home planet arrives on Earth.

In the near future, humans have discovered a fourth dimension, Dimension W, and a supposedly infinite source of energy within. In order to harness this profound new energy, mankind develops advanced "coils," devices that link to and use the power of Dimension W. However, by year 2071, the New Tesla Energy corporation has monopolized the energy industry with coils, soon leading to the illegal distribution of unofficial coils that begin flooding the markets. Kyouma Mabuchi is an ex-soldier who is wary of all coil-based technology to the extent that he still drives a gas-powered car. Kyouma is a "Collector," individuals with the sole duty of hunting down illegal coils in exchange for money. What started out as just any other mission is turned on its head when he bumps in Mira Yurizaki, an android with a connection to the "father" of coils. When a series of strange events begin to take place, these two unlikely allies band together to uncover the mysteries of Dimension W. [Written by MAL Rewrite]

Ceres was a tennyo (Celestial maiden) who came down from the heavens to bathe in a stream. She hung her hagoromo (robe) on a tree nearby, which was her key to returning to the heavens. But the robe was stolen and the man who had stolen it forced her to become his wife, thus producing a family full of human and tennyo blood mixed. Now, in modern day time, Aya Mikage is a descendent of Ceres, and has quite an amount of tennyo blood. On her 16th birthday, she and her twin brother, Aki, are thrown a party. At the "party," Aya's grandpa plans to kill her, for she has tennyo powers unlike the rest of the family, and can actually become Ceres herself and destroy the Mikage family. Aya, however, can switch back, so this transformation happens quite frequently. With protector Yuuhi by her side, it is up to Aya to control Ceres and keep her from coming back, but her relationship with an ex-worker for her evil grandpa may be a distraction.