Fuhoni desu ga, Ryukishidan ga Kahogo desu

Leonora, the second princess of the Kingdom of Lybra, assumes the alias "Nora" to secretly join the Dragon Knight Order of the neighboring kingdom, Wahnrein, in order to keep an eye on her younger sister, who has married the crown prince. Her cover is at risk when Harvey, the commander of the Dragon Knight Order and a renowned figure known as "Dragon Slayer," discovers her true identity. In a further twist, she forms a contract with the dragon named Aksel.