Fuhoni Desu ga Ryuukishidan ga Kahogo Desu

The second princess of the Kingdom of Lybra Leonora decides to venture the perilous undertaking of infiltrating as Nora into the Dragon Knight Order of the neighboring kingdom Wahnrein to watch over the apple of her eyes her little sister who was married off to the crown prince of Wahnrein However she soon gets into a tight spot as the the commander of the Dragon Knight Order Harvey who is known throughout the continent as Dragon Slayer and finds out about her real identity
Furthermore she seals a contract with the dragon Aksel