Ikki Kurogane is the lowest-ranked Blazer at Hagun Academy, branded "the Worst One" for his feeble magic in a world where warriors can forge weapons called Devices from their souls. His routine collapses when Stella Vermillion, the A-rank princess of Vermillion, transfers in and is assigned to share his room. After an awkward first meeting, the two settle a duel whose loser must obey the winner, and Ikki begins training toward the Seven Star Sword Art Festival alongside Stella.