"Hey, Ryuu. Want to go to the school swimming pool with me tonight?" On a certain day, after school, year one student Yakumo Ryuu received this kind of invitation from Nanami Yuki.
In a mysterious academy town where people with strange power gathers, the student council president who is known as the strongest in history is currently sealing off the academy, all the students are under house arrest. Only by defeating five power user in a "duel" will they be able to regain their freedom.
Those who choose to rebel are known as heroes, but Ryuu who can only "create a doppelganger within three meter radius" is completely unsuitable to engage in battle, so he is one of the numerous spectators remaining.
However, on one particular day, since Ryuu obtained a sword by chance late night in the campus, the power level of the academy has been completely toppled, Ryuu stood up as a traitor! Using a sacred sword and demonic sword to open his path, let the academy battle begins!