Mia Clementis acts as primary maid and escort to Princess Feena Fam Earthlight of the lunar Kingdom of Sphere. Residing with the princess during Feena's homestay on Earth with the Asagiri family, Mia diligently handles household responsibilities like cleaning and cooking with dedication and passion. Generally shy and reserved, she possesses strong protective instincts towards Feena. This protectiveness sometimes leads her to act hastily or overstep boundaries when she perceives a threat to the princess's safety or well-being. Despite her servant role, Mia shares a close, trusting relationship with Feena that transcends duty into genuine friendship. Her background identifies her as a human from the Moon, primarily defined by her service within the lunar kingdom's structure, with specific family or past details largely undefined.

Expanded narratives in alternate versions, specifically the PlayStation 2 and PlayStation Portable ports, explore Mia's role further through an optional romantic storyline where she becomes a potential love interest for protagonist Tatsuya Asagiri. This route develops her character as she navigates her own feelings while maintaining unwavering loyalty to Feena, revealing a more personal dimension to her duties and relationships. Her connections extend to other lunar figures such as Karen Clavius, reinforcing her integration into the broader Earth-Moon diplomatic and social context. Mia's interactions sometimes involve comedic situations arising from her earnest, occasionally overzealous actions, particularly when misjudging scenarios involving Feena's independence or safety. Across adaptations, her core identity remains consistent: a devoted caretaker whose actions, though occasionally marked by naivete or overprotectiveness, stem fundamentally from deep loyalty and affection for those she serves.