Swallowtail Dragons are graceful and quick flyers, much like their namesake bird. They are capable of precise aerial acrobatics, and can reach very high altitudes. Because of this, humans observing these dragons are often astonished at how large they are when confronted up close. A Swallowtail’s diet consists of insects and small mammals plentiful in temperate forests. These dragons are also made remarkable by their paper-thin wing membranes, which allow light to pass through, creating an astonishing effect on starry nights.

Dragons are highly-intelligent reptilian creatures that—from a human perspective, at least—appear to live forever. Many different varieties of dragon exist, each with their own unique qualities, habitats, and behavior. Adolescence in dragons is usually marked by the growth of a hatchling’s wings, although not all breeds of dragons grow wings and some breeds have other traits that indicate the beginning of maturation. In Galsreim, dragons and humans coexist peacefully.

Usuki Tsubasa was born with a birth defect that affects his wings. Because of his breed, his wing membrane is already thin, but because of the defect the membrane is even thiner. It is so thin that he has never been able to fly and if he tried too hard, it would rip his wings straight through. His full grown adult dragon wings could not even lift the weight if a hatchling. The other dragons in his group know this and they help feed him because he cannot hunt very well on the ground and since he cannot fly, he cannot get enough food.

His name means thin wing.