The World's Finest Assassin Gets Reincarnated in Another World as an Aristocrat, Vol. 5 (manga)

An army of orcs is invading, and although the academy is doing its best to fight back, its walls are crumbling. While Dia and the others battle the main force, Lugh chases after the Hero, Epona. Can the two of them take down the demon that’s leading the monsters?