Rosemarine holds the position of student superintendent at Lacombrade Academy, wielding considerable authority among the students and earning the moniker "White Prince" through his role and bearing. As a distant relative of the Cocteau family, he shares lineage with Gilbert Cocteau. During his youth at age 15, Rosemarine endured sexual assault by Auguste Beau, establishing a traumatic connection to Gilbert's primary abuser. This shared victimization informs Rosemarine's subsequent actions; he initially cooperates with Auguste's manipulation and control over Gilbert, perpetuating the cycle of abuse within the academy.

Despite this alignment with Auguste's schemes, Rosemarine forges a genuine connection with Serge Battour after Serge arrives at Lacombrade. This friendship gradually reshapes his perspective, culminating in a decisive shift in allegiance. Ultimately, Rosemarine chooses to assist both Gilbert and Serge in escaping the academy, facilitating their flight to Paris to evade the oppressive forces directed by Auguste and the school establishment. This action marks a significant departure from his earlier complicity, highlighting the complex conflict between his past trauma and burgeoning empathy.