Mullan Sero is a knight of the Galbraith ducal house and serves as the captain of the dragon knights. He is one of the trusted subordinates who, alongside the butler Chaos, supports Aristide Rogier du Galbraith, the head of the house. His background is that of a loyal retainer, having earned his position through both skill and dedication. His personality is bright, humble, and cheerful, making him well-liked among the soldiers under his command. He is also affable and approachable, which allows him to quickly form a warm friendship with Melphiera Marchalrayd, the female lead, after she becomes involved with the Galbraith household. His motivations are rooted in loyalty to Aristide and the Galbraith family, and he works diligently to support their goals and protect their interests. In the story, he serves as a reliable ally and aide, often accompanying Aristide and assisting in various tasks. His key relationships include his commander Aristide, his fellow subordinate Chaos, and Melphiera, with whom he shares a genuine camaraderie. While he does not undergo major personal development, his role helps to integrate Melphiera into the Galbraith circle and demonstrate the strength of the household’s bonds. As a dragon knight captain, his notable abilities include combat prowess, leadership, and likely the skill to ride and command dragons, though specific feats are not detailed. He is depicted with short blonde hair and golden eyes.