Easygoing Territory Defense by the Optimistic Lord: Production Magic Turns a Nameless Village into the Strongest Fortified City (Manga) Vol. 8

THE FLAMES OF WAR THREATEN A CHILD PRODIGY'S EASYGOING LIFE!
The neighboring Kingdom of Yelenetta launches an attack on Marquis Fertio’s territory! Agreeing to help, Van brings reinforcements, thinking that the battle will already be won by the time they get there. However, when Van arrives, he finds Scudet—the once impregnable fortress city—reduced to flames. With his father cornered on the battlefield, Van and his companions must use all their resources and then some to face down the enemy.