In JJK With Naruto Powers - Chapter 132: New Zenin Clan Leader

Xu Jun finally defeated the BOSS–the Dark Demon King, in this stand-alone, virtual reality game. When he wanted to go out to browse Weibo and express his mood, he suddenly encountered a game BUG and immediately passes over to the game world.

He became the man who finally took down the Great Demon King in this world. Gratifying! The attention of millions of people!

……However, he did not know the development of this world was not the same as the game, the Demon King did not die, rather his soul entered into Xu Jun’s body; this Demon King knows of all the stupid things Xu Jun does everyday…….

- Description from Novelupdates

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.

Li Chengfeng, a scientific research genius of the 21st century, traveled through the Tang Dynasty and turned into Li Shimin’s six-year-old son?

  In the god-given god-level bear boy system, Li Chengfeng grabbed Li Shimin’s beard and started mad at Fang Xuanling and Du Ruhui, but there was nothing they could do about it.

  Li Chengfeng used his genius scientific knowledge to solve natural disasters by diverting water from the south to the north, and the hybrid rice developed by him can produce 2,000 catties per mu.

After destroying the Turks and subduing Goguryeo, Li Chengfeng was conferred the title of God King of the Tang Dynasty at the age of six.

It can be said that Mo Chou has no confidant in the future, who in the world does not know the king?

- Description from novelbuddy