In a certain empire, humans and dragons live together. Dragons are rare, with only a dozen or so in the entire world. Five of them reside within this Empire. Guest is one of the dragons living in this Empire. Dragons can take human form at will. After transformation, dragons have a human appearance with two horns and slit pupils like a reptile. Dragons in the Imperial Knights are encouraged to live in human form except during combat. Dragons are generally managed by the Empire and work in the Knights due to their high combat power. Consequently, they are frequently sent to the front lines. They form a contract with a human knight and live and work together as "partners." Human partners for dragons are selected based on their abilities and character. Knights live in dormitories with assigned rooms. Contracted partners live in the same room. The size varies by rank and contribution, but the estates for dragon pairs are more luxurious than those of ordinary knights. The nature of the partnership varies for each pair. Because dragons are rare and possess high strategic value, they are treated with great care. However, they are also feared for that same power, and many harbor resentment toward them in secret. While other countries possess dragons, few manage them as thoroughly in a military and social sense as the Empire does. >

While it is called a "contract" to sound formal, in reality, the majority of a partner knight's job is "keeping their dragon in a good mood."