A richly romantic action-adventure fantasy, set in a world where retro-futuristic vehicles permeate the skies. Against this lavish background are the lives of young and heroic van ship sky porters - Claus and Lavie - who are forced to take on the mission to deliver a mysterious girl, Alvis, to the battle ship Silvana. Before they know it, they become entangled in an aerial adventure between two countries gripped in an eternal war of magnificent air battleships.

As the world is in the middle of an industrial revolution, a monster appears that cannot be defeated unless its heart, which is protected by a layer of iron, is pierced. By infecting humans with its bite, the monster can create aggressive and undead creatures known as Kabane. On the island Hinomoto, located in the far east, people have built stations to shelter themselves from these creatures. People access the station, as well as transport wares between them, with the help of a locomotive running on steam, called Hayajiro. Ikoma, a boy who lives in the Aragane station and helps to build Hayajiro, creates his own weapon called Tsuranukizutsu in order to defeat the creatures. One day, as he waits for an opportunity to use his weapon, he meets a girl named Mumei, who is excused from the mandatory Kabane inspection. During the night, Ikuma meets Mumei again as he sees Hayajiro going out of control. The staff on the locomotive has turned into the creatures. The station, now under attack by Kabane, is the opportunity Ikoma has been looking for.

The rookie sky pirate Coud finds an unusual cargo in his mates' cargo hold: Ren, an "Edel Reid", a race prized by humans for granting special combat power to their partners through "Reacting". He quickly discovers, however, that Ren is even more prized than he expected. The pirate ship is visited by members of the Edel Reid Complete Protection Agency "Arc Aire", who try to purchase her. When Coud refuses, the ship is suddenly attacked by a mysterious force, and Coud's captain charges him with Ren's protection.