Sebas is the longstanding butler of the Jamil noble family, serving Reinbach Jamil since Reinbach's youth. His duties extend beyond traditional butler roles, as he is also a top-tier spatial mage. This expertise led him to mentor numerous apprentices over the years, primarily sons of nobles and family retainers, aiming to meet the high standards required for distinguished households. However, this mentorship met repeated disappointment, with most apprentices failing to achieve proficiency.

His instructional approach shifted upon encountering Ryoma Takebayashi. Teaching Ryoma spatial magic, Sebas was surprised and delighted by Ryoma's extraordinary aptitude and rapid mastery of complex techniques, marking a rare positive turn in his teaching history.

Beyond instruction, Sebas actively supports the Jamil family's activities, participating in field missions. He accompanies the family during training exercises in locations like abandoned mines, offering both practical assistance and magical support, such as joining operations to clear monsters.

He also aids the family by cultivating connections and managing resources. He facilitated Ryoma's education by introducing him to trader Serge Morgan, enabling Ryoma to discreetly sell his alchemical creations, demonstrating Sebas's involvement in both household affairs and broader social networks.

Personality-wise, Sebas embodies the disciplined professionalism of a high-ranking servant. He maintains composure while showing genuine investment in his charges' success, particularly evident in his reaction to Ryoma's progress. His past disappointments underscore his commitment to upholding the family's prestige through effective service and training.