Valentine eggs are only seen once a year. Adults’ mating seasons are very short, usually spanning a few weeks in the mid-to-late winter. These dragons were once reputed to be omens of good luck in love.

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.

Yui is an uncannily cheerful dragon, sometimes to the point that it's really creepy, usually seen bouncing around and telling everyone about how beautiful and amazing the world is. She can always find something positive about any situation, no matter how bad it is. Although she is highly optimistic and is great at cheering other dragons on, she isn't that confident about herself, and is very bad at resisting Glorious Sun and Syalis's jeering. She has earned the trust of just about every dragon in the cave and loves teaching the hatchlings to fly and to use their telepathy better. Yui likes to daydream and to go out and fly and look at all the beautiful flowers and trees. She has a small collection of pretty rocks and scales she has found that she will show to anyone who asks. Ateqozz thinks some of them are mana crystals. She will trust just about anyone, but don't misuse that trust. Once she gets a grudge, there's no way that person is ever getting her trust back!