Serge serves as Mai Viole's dedicated battle butler, later continuing his service when she becomes Mai Shinomiya. His primary duty is ensuring Mai's safety and providing unwavering support during her activities, including her engagements as the purple soldier in card battles. He maintains constant vigilance, offering heightened protection when Mai acts independently or faces significant threats.

Serge's loyalty remains steadfast throughout Mai's evolution. He continues serving her seamlessly during her transition in the sequel series, where she retires as a public net idol, adopts her real surname, and alters her appearance. His service persists without interruption even when Mai temporarily leaves Dan Bashin's group to align with Barone and the mazoku faction, upholding his duties consistently across these changes in her affiliation and objectives.