Otome Game Sekai wa Mob ni Kibishii Sekai desu: Kyouwakoku-hen

Although Leon saved the kingdom—and even the world—from crisis, he hears from Marie that the game actually has a sequel.
If the same kind of events that Marie triggered were to happen in the Republic as well, the world could be headed toward destruction once again.
To prevent that crisis, Leon and Marie, along with the others, arrive in the Republic of Alzer as exchange students—but then...!?