Rosalia attends music school with Alice, her class situated next to Alice's. She shares a close friendship with Sania, often acting as a calming presence and guardian figure within their group. Rosalia possesses a gentle demeanor and takes a sincere interest in Alice's musical journey, specifically helping her rediscover a particular melody troubling Alice's memory. This original storyline focuses on Alice's experiences before entering the castle realm, where Rosalia and Sania offer emotional support during Alice's struggle to recall the tune. Within the castle's dreamlike environment, Rosalia emerges as part of Alice's subconscious exploration. She actively joins Alice and Sania in searching for music, using her violin playing to navigate the castle's mysteries and aid memory recovery. Her musical abilities help progress through the castle's challenges, with her integration into the fantasy narrative focused solely on supporting Alice's journey. Rosalia's personality is marked by initial shyness and reserve, though her reserve may seem aloof at first. Despite this, she forms a meaningful bond with Alice through their shared effort to recover lost memories. She demonstrates quiet determination and resourcefulness confronting the castle's challenges, channeling her skills and music to aid others. Her character arc centers on this supportive role in both reality and the dream world.