Aizawa Katori is bound by an unusual rule at her school that forbids female students from interacting with the male scholars in the neighboring institution. To enforce this, all girls are required to wear masks. Katori chooses a horse-head mask but remains resolute to reconnect with her childhood friend and love interest, Shinra. Although Shinra has feelings for Katori from the beginning, he remains oblivious to her true identity behind the equine disguise.