The Magic in this Other World is Too Far Behind! Volume 10 by Gamei Hitsuji

With Suimei back in his own world temporarily, Reiji’s party goes to Astel to report on recent matters to the king. But while there, they suddenly find themselves besieged by a demon army that appeared out of nowhere!

Reiji sets forth with his Sacrament in hand, but Astel’s army is still on the ropes. Will Reiji and his party be able to hold back the invasion long enough for there to still be a world for Suimei to return to?