Jacques Dren

A notorious upperclassman at Lacombrade. He was crazy about Gilbert and had a duel with Max Blough, supervised by Rosemariné, to decide who would have him, which he lost. Gilbert ropes him into a scheme to get rid of Serge as his new roommate, but he's betrayed by Gilbert after he fails. He's expelled from the academy by Rosemariné and Gilbert is made to look as if he had nothing to do with the incident.

(Source: Kaze to Ki no Uta Wiki)