MTL - I Can Level Up By Staying Idle - Chapter 20 I'll give you good pointers

A modern Japanese man reincarnated into a game as Welner von Zeavert. Though he reincarnated as a noble’s son, he is neither the main character nor the hero of this world. He become someone who didn’t even appear in the game.Plus, with only [Spearmanship] as his skill, he can’t even join the hero party to clear main story.His small advantages are the fact that he became the hero’s friend and his father’s rather high status. He’s nothing but a supporting character of the story.He noted the game story that he knew from his past life, used it, along with his authority and influence as a noble, to survive from demon king army.But, without realizing it, the knowledge from his past life and his memories of the game story affected the world. He saved people that should have died and took care of events that didn’t appear in the game.With that, he carved history of this worldThis is not a story about the hero. This is a story about struggle and effort of a young noble.

The unparalleled Demon King Ye Xuan, who was able to heal the death or the living alike and holder of the medicine Holy Scripture, was betrayed and killed by his fellow Demon Kings. But he reincarnated into the body of Ye Xuan, the prodigal son of the Ye family and vowed to himself that he would return to his peak and take back everything that belonged to him!

- Description from Novelupdates

Shi Hao, a young man, managed to turn the tables on a powerful figure trying to possess him. He gained countless cultivation techniques, martial skills, formations, alchemy knowledge, and talisman arts, setting him on a legendary path.Now, every genius and tyrant must bow before him.Those who refuse? They'll be eliminated!

After dying in the world of One Piece, he was reincarnated once again this time as Neji Hyuga. But fate was no kinder here. With his father dead and the cursed Caged Bird Seal looming over him, for his survival he made a ruthless decision....