Floating around an endless sky, giant creatures revered as gods carry on top of their backs islands with entire civilizations.
Hoshina's clan lives on a particularly aggressive creature called Ikusagami, who often attacks the others. Thus, as per the wish of their god, it's people have adapted to a fighting lifestyle where being a great warrior is considered the highest honor.
In a different island where the concept of war has long ago been forgotten, Kaji is constantly starting up brawls with anyone who gets on his nerves. So when these peaceful days he thinks he hates are traded for the hell known as war, he's the first one to fight back.
And so, when the girl who wants to become a warrior and the boy who doesn't know peace meet, both are challenged in ways they could never begin to imagine.