Genjitsushugisha No Oukokukaizouki

Souma Kazuya is a new hero who needs to save his land from Demon King: the enemy has become the owner of over a fifth part of the land. First of all Souma visits the ruler of his country, promising to make it rich and strong. Unexpectedly the ruler gives him his crown. Now Souma Kazuya asks for help from all his friends to make new country with new nation. But will it be successful?