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.

Despite his incredible bashfulness, Atsuhiro Akkun Kagari has landed the girl of his dreams: the sweet and loveable Non Katagiri. However, his embarrassment for affectionate acts—from giving compliments to exchanging a kiss—causes him to act harsh and downright mean to Katagiri in their day-to-day lives. But Akkun is still very much a boy in love; he shows his admiration for Katagiri in his own way. From tailing her in order to take her picture to eavesdropping in on her conversations, he ends up stalking his own girlfriend. Luckily enough, Katagiri finds Akkun's actions cute and endearing, and knows he doesn't really mean any of his insults. Even if their close friend, Masago Matsuo, finds their dynamic a little odd, Katagiri loves her sweet tyrant just the way he is.

The Sailor Guardians and their leader, Sailor Moon, continue their duty of protecting Earth from any who would dare cause it harm. However, Sailor Mars' apocalyptic visions and the appearance of two new guardians—Sailor Neptune and Sailor Uranus—signal that a new battle will soon begin. These newcomers seek three Talismans that are inside the Pure Heart Crystals within human beings. Once brought together, these objects form The Holy Grail, a magical relic with extraordinary abilities. They want to use the Grail to save the world, but an evil organization known as the Death Busters seeks its power for their own desires. The removal of a Talisman from a person's Heart Crystal will cause their death, something that Uranus and Neptune see as a necessary sacrifice to form the Grail, while Sailor Moon and her group deem it unforgivable. But can any sacrifice be worth the cost if it saves the lives of the entire human race?

Upon hearing news that his mother was on verge of death, Haru Kaidou—the eldest son of the family—flies all the way to Canada. The moment he arrives, he learns that not only did his mother fool him, but he is also supposed to take care of his adoptive brother, Ren Kaidou, an antisocial kid who feels more comfortable around dogs than people. Due to his new brother's distrustful nature, Haru initially has a hard time reaching out to Ren but their relationship eventually grows. He makes a promise to Ren: they will live together in Japan after Haru graduates from high school. However, due to an unfortunate accident, Haru loses all memories of the summer they spent together, including the promise he made. Five years later, expecting Haru to keep his promise, Ren arrives in Tokyo; but to Haru, Ren is just a random boy claiming to be his brother.