Jack Jeanne: Univers Kageki Gakkou to Tsuki no Michishirube

Kisa Tachibana is a girl who is fascinated by the world of theater. Kisa's older brother, Keiki, is her idol. Everyone who aspires to a career in the theater dreams of knocking on the door of the Univeil Opera School, where Keiki is a star performer who has been called Univeil's greatest treasure. If only Kisa could one day stand on the same stage as him... but one day, Keiki disappeared without a trace. To make her dream come true, Kisa enrolls herself in the Univeil Opera School. However, Univeil is supposed to be a boys school... So she hides the fact that she is a girl, and plays the role of a boy.... This is a tough role for a rookie performance! (Source: J-Books, translated)