For eighteen years, Runa's universe has been a gentle, silent sea of stars, viewed from within the living body of Weltorm, the last of the ancient, sentient star-whales. Raised in the heart of the magnificent being who became her parent and guardian after the death of her scientist parents, Runa knows only a life of symbiotic harmony, communicating through a silent, telepathic song and exploring the endless, bioluminescent corridors of her home.

But their peaceful existence is shattered when a dissonant note of decay enters Weltorm's song: a terminal decline known as the Stagnation. Weltorm's only hope for continuing his lineage is a transformation that would erase his individual consciousness forever—a fate he fears more than death. As his light begins to fade, a new, more immediate threat appears: a ruthless corporate vessel, the V.C.S. Archive, arrives to claim the dying star-whale's priceless memories as a salvageable asset.

Driven by a desperate love, Runa discovers her parents' hidden research—a path to a mythical "Song of Ascent" composed of cosmic harmonies scattered across the galaxy. Believing this song is a cure, she embarks on a perilous quest in her parents' small ship, the Stargazer, leaving the safety of Weltorm for a noisy, dangerous galaxy she has never known. But as the sinister Veridian Corporation hunts her at every turn, Runa uncovers the terrible truth: the song is not a cure, but a beautiful, heartbreaking lie designed to grant a mercy she may not have the strength to deliver. Now, Runa must carry the weight of an impossible choice: allow her guardian to fade into a terrifying oblivion or save his legacy through an act of profound betrayal.