Toua no Mahoutsukai Mahou Gakkou to Noroi no Shoujo

Mia, a girl who "fell" into Finzel Magic School, the nation's top magic school, has lost all her memories. Absalon, the school nurse who took Mia in, suggests she infiltrate the school. If she can become a member of the top student group, the "Opera," she will gain access to the Royal Library. This should also solve the mystery of her amnesia. Thinking, Mia is captivated by the magic of Bruno, an upperclassman in the Opera, and decides to study there. Bruno is wary of Mia's true identity, but his straightforwardness eventually convinces him to support her school life. However, her overwhelming magical power leads to a challenge to a duel by Katrina, a young lady from a noble family... (Source: Kadokawa, translated)