The Ex-Hero and the Next Demon King: Walking to the Demon Castle

The long war between the Hero and the Demon King finally came to an end through a mutual truce. When the Hero proposed "his own defeat" and "peaceful rule under the Demon King," the world began heading toward reconstruction under the Demon King's guidance. Around that time, Abigail, the daughter of the Demon King, is ordered by her father to take the defeated hero and carry out a certain mission—but just what could that mission be...?!