Naruto System in One Piece - Chapter 486

The formless ancient world was infested with despicable demons. They hunted and feasted on mankind, keeping the human civilization constantly in a weak and suppressed state.

During the first known year, a magical mountain descended into the world from the realm of the Gods. Carved on this enormous mountain was a message: ‘Heaven Prevails’…

After the Grand Descent, a name that was given to the descending of the mountain, the Three Great Sages made their ways to Mystic Mountain where they learned to harvest what we now call magic, establishing the Mystic Cults and eighty-one sacred shrines to help aid mankind with the cult’s mystic powers against the eternal fight to the death with demons.

- Description from Novelupdates

The dark BOSS, who had the privilege of being the last living person on the planet, and the second-oldest brother on the planet was born again.

What should he do after he was born again? Was it to rule or destroy the world?

BOSS said that he was not interested in these, he just wanted to die. In order to let the boss who was bent on ending his own life live, he was omnipotent, and he will be comfortable with the boss, and then helplessly find out…

BOSS was more and more wrong with the style of painting!

- Description from Novelupdates

Year 2056, in a city in the Yuan Jiang Su Jin area. On top of a ruined, shattered six story residential apartment sits a teenager wearing a combat vest, militaristic trousers, and alloyed battle boots. On his back is a hexagonal shield and equipped is a blood-shadow battle knife. He sits there silently on the edge of the roof. At this time, the sparkling sky was shining and there was a refreshing breath within the air that blew towards him. However, there was only silence within the ruined, deserted city, with an occasional howl that makes your heart skip a beat.

Demon Lord! A symbol of terror and evil! Killing and death are associated with him! In a magic country, a being was summoned. This being was the most demon lord unlike of all demon lords in history.

“Your majesty demon lord, please sign a document here. But please be careful not to put your hand at the wrong place.”

“Your majesty Ya Lin, human army are invading us but I will protect you with my life!”

“Hate you! Don’t come closer! You are a real pervert demon! I hate such demon the most!”

O God, what is this? I just wish to be an ordinary person with carefree life and stuffed with food till death. Why I am the one who will become the future husband of the demon princess, the future demon lord? And also completing a near impossible task ——-resurrecting my mother-in-law? Luckily becoming a demon does have its own benefits, granting each demon ability to cultivate skills.

However, what type of circumstances are this, mission going to other worlds and conquer them?

- Description from Novelupdates