はるのあしおと The Movie - 桜鈴奪還

One day the else so peaceful mood in the Ourin Gakuen suddenly changes. Kusunoki-sensei, the so-called subheroine, along with most of the students takes over the school after a coup d'état. The principal is beaten and now it's up to Yuu Sakurano, Yuzuki Kaede and Nagomi Fujikura to take back the school from her and return it to the former peaceful days. This is the start of a full-scale war, one that this school has never seen before.