Naruto: The Mist Within - Chapter 69 - : Seals

Who, in the ancient mythology, held an artifact and killed the first emperor of the human race?

Who, at the beginning of ancient times, closed the gate of the God Realm, Jedi Tiantong?

Who set a lifespan limit of only one hundred and thirty years for the people, and even the Great Emperor was not spared?

Who, turned into a black hand that covers the sky for eternity, shrouded the world?

…

Yang Shou on Earth: “Yes, yes, I did it all, I just want to live.”

- Description from novelbuddy

Crossing to One Piece world, he became Roger’s younger brother.

[Class changing to the hidden class, Demonic Swordsman.] [You are the first one to discover the hidden dungeon.] [You are the first one to discover the hidden…] [You are the first one…] [You are…] I’m a gamer who uses ESP.

Kai of the Sorcerer’s Tower is one of the last mages left, barely surviving in a world ruled by creatures of the dark — where the era of mages ended, and most of the lands got contaminated with dead mana. To save his world and fulfil his master’s last wish, he put himself through a forbidden ritual, risking his soul being ripped into pieces to make his way into the past. In an era with abundant mana — an era yet to enter the Golden Era of Magic. Things go wrong, of course, as they always do, and he finds himself thousands of years before the world fell to mana contamination — in the body of a young lord, Arzan. All is not well, though, as the young lord was murdered by someone right at the cusp of a beast wave threatening the territory, while larger threats loom on the horizon. There was a lot to do for Kai to regain his former strength in this time of primitive technology, but then again, he might just be able to change that.