Chivalry of a Failed Knight

Ikki Kurogane attends a magic-knight academy where students fight using Devices forged from their own souls. His own talent is at the bottom of the class — the school's official lowest-ranked Knight, nicknamed the Worst One — but his sword work and his refusal to lose put him further than his profile suggests. He is caught changing in the dorm room he didn't know was his new roommate's by Stella Vermillion, the visiting princess of another country and her year's top-ranked Knight. She challenges him. The loser of the duel will obey the winner for life. They duel. The school year continues.