Ikaros, the half human, half Aviatte boy living in the Aviatte cloud city Parnaia has always been viewed as an outcast because of his parentage. Daedalus, his father, is a well-known architect and craftsman who often travels down to the earth-bound cities of the humans, and the subterranean world of the Hadeans. However, because his mother was a human woman, Ikaros was born without the wings characteristic to the Aviatta subspecies. When he turns eighteen, Daedalus sends young Ikaros down to Earth in search of his mother, and along the way he meets Hephaestus, a Hadean girl with a talent for metalworking. Together, they must track down Ikaros' missing parent as well as learn about the world that separates Ikaros' cloud cities from Phae's underground settlements.