The Fruit of Evolution (Light Novel), Vol. 11: Before I knew it, my life had it made!

After saving the Valshe Empire from near ruin, Seiichi finally returned to the Kingdom of Winburg. However, as soon as he arrived, Routier and the others were already heading in the opposite direction toward the ancient dungeon where the Demon King had been sealed for ages.
Their journey swiftly turned dangerous. On the road, they faced monstrous beings so powerful that their levels didn’t even show upâ€"an obvious sign that something was seriously wrong. When they reached the depths of the dungeon, an even more intimidating figure waited: Vitor the Resonant, a divine guardian sworn to protect the sealed domain. With shadows closing in and tension mounting, their battle with him erupted into a fierce fight.