In the era of floating cities where humans avoid the clouds, sound is a precious resource that can be solidified, traded and forged. Leah, the top sound alchemist, hates all noise due to a childhood accident, and has spent her life pursuing the creation of the ultimate device that can completely silence the world. However, a collection mission deep into the acid rain clouds caused her to have a fatal resonance with a "Wailer" storm that had consciousness and was composed of hundreds of years of painful cries. In her eyes, the sky was dyed with an eerie green that only she could see, and the storm tracked her like a vengeful ghost, intent on swallowing up all sounds. As the investigation deepens, Leah discovers that the bloody original sin of the rise of the Sky City civilization is sealed in the roar of the storm, and is also closely connected to the truth about her father's death. She must choose between the silence that annihilates history, or the destruction that confronts the truth. This is a fantasy story about sound, memory and redemption, telling how a lonely listener forged the curse of civilization into a requiem of redemption.
