Waterhorse Dragons received their name due to their horse-like physique and endearing behavior. They are capable of surviving out of water, and when on land their skin secretes a gelatinous goo to retain moisture. However, their large paddle feet are better suited for swimming, and waterhorse dragons tend to move very awkwardly when on land. Waterhorses are very friendly dragons and enjoy playing with humans.

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.

Koumineko has an unfortunate condition. He produces much more slime than is normal for a waterhorse, so he drips puddles of it everywhere he goes. Apart from the irritating, slightly sticky trail that persistently follows him, he often suffers from dehydration, and needs to drink more than any dragon should. That is, any dragon without a slime-gland problem. On another note, he grew up near the sea, and has a great liking for seagulls. For this reason, he is one of the few dragons in the cave who actually likes Kawaneko, who is, in fact, his mate.