This anime takes place in a fantasy world called Prestale, which has an atmosphere very similar to Europe around the start of the Industrial Revolution. The key difference being aviation technology in Prestale has already far exceeded even what we have today. At the beginning of the series, we learn that the world is in turmoil due to a war that is being fought between the two main countries: Anatore and Dusis. Terrible weather has forced Dusis to resettle, but Anatore won’t tolerate it.
We first meet our heroes, 15 year olds Claus Valca and Lavie Head, living alone in the small town of Norikia in Anatore. Several years ago, their fathers were a renowned team of Vanship (A small plane) pilots and flew many important missions. On one such undertaking, they are forced to fly through the Grand Stream, an infamous constant storm that separates Anatore and Dusis, and end up being killed. After hearing about the crash, Claus and Lavie decide to repair their father’s plane to start their own vanship flying business with the dream that they can one day challenge the Grand Stream and come out alive.
The vanship missions they are assigned get quite dangerous; as one has our pair flying through the middle of an intense aerial battle between Anatore and Dusis. Later Claus and Lavie end up being entrusted with an 11 year old girl, Al, and become drawn into the war as part of the crew of the battle ship Silvana, led by mysterious man Alex Rowe. Who is the real enemy threatening the world of Prestale, is it Anatore, or Dusis, or the ominous Guild that is after Al for some reason.