Vampire Dragons are members of the undead. They sustain themselves by drinking the blood of others. It is said that they are only “alive” at night, and seem dead or asleep during the day, as they cannot endure sunlight for long periods of time. Vampire Dragons can only reproduce by changing the eggs of other dragons, puncturing the shell with their fangs and injecting venom that kills the baby inside.

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.

Both her family and given name is Japanese. "Kurosu" consists of the two kanji letters "kuro" for "black" and "su" for "master, lord, master, principal, main thing". "Yuuki" means "gentle princess".

She is usually a cheerful dragon who enjoys jokes, regardless if she is told one or if she humours others. Given the situation, she can also put on an authoritative face if, showing her emotionally maturity and thoughtfulness.

However, she is completely lacking in charisma, failing to be a convincing leader. The only reason why other vampire dragons show respect towards her is her legacy and ancestry, having a "true vampire dragon" as grandfather.