Sayaka Dejima fulfills the role of personal maid to Aria Shichijō within the Shichijō household. She consistently presents a professional and polite demeanor, usually attired in a standard maid uniform with her dark hair secured up. Her tone remains controlled and respectful, adhering to role expectations, though flashes of overexcitement or immaturity occasionally surface. Sayaka handles the diverse tasks required for Aria's care with competence, showing particular skill in cooking and laundry duties. Her proficiency in laundry connects to a personal interest in unwashed clothing, specifically items worn by Aria, indicating a particular fetish.

She bears responsibility for safeguarding Aria's chastity belt, holding exclusive control over access to its key. This duty necessitates Aria requesting the key from Sayaka for fundamental activities like using the bathroom. Sayaka exhibits protectiveness concerning Aria's well-being and personal boundaries. Her fixation extends to items Aria has touched or worn, often manifesting as a desire to undress her. Sayaka is also portrayed as possessing experience in sexual practices, specifically noted as a dominatrix.