The World's most Overpowered Side-Character

After saving one world from a Demon God and earning the trust and devotion of a perverted goddess, Sol is rewarded with all his powers intact and sent back home with the goddess accompanying him as his personal slave. That was supposed to be the end, the Demon God was supposed to be his last great trial. However, they are both summoned once again to an even more doomed world, almost immediately after returning to Sol's. This time around, Sol refuses his role as hero. Unable to find rest, he turns his wrath to the pantheon of gods in a spiteful quest to become the strongest being in existence, followed by his slave who took his place as hero. Battles await, secrets of old begin to scurry into the light when the world as he knows it begins expanding beyond the visible horizons of reality and deep into the fringes of eternal darkness. Terrible consequences lay beyond the borders of the known.