Seven Sisters!

A student named Minagawa Ichiri prefers to stay out of trouble by avoiding action, but he can't escape being transferred to a new school due to his parents' work. This time, it's Reimei Academy, part of the prestigious "Seven Sisters." During a tour with the vice president, Kirishima Shitone, an attack happens. The attacker targets individuals with long black hair and swords, seeking revenge on "Double Edge," who used a power called "Idea"—activated through a device known as a "Codec"—to bring principles into reality and kill her best friend.