My Two-sided Cultivation: Starting From Collecting Experiences - Chapter 645 - The Nightmare of the Six Royal Clans

What happens when a fanfic author with a habit of lying and scheming suddenly finds himself as a self insert during Duelist Kingdom? What happens when you have Yugi, Joey, Kaiba, and the rest encounter someone who knows all about every major player in their saga... and sees no problem with abusing said knowledge? Chaos, dear reader. Sweet, sweet chaos

The strongest Hero in history, Nakamoto Keisuke.

He was summoned to another world in the spring at the age of fifteen years old, and when he successfully defeated The Demon King, he was already thirty-two years old. He had finished his role in another world and returned to Japan, but the reality that had been waiting for him was, “Middle school graduate with seventeen years of blank period” label. He couldn’t find a decent job and had no choice but to spend his days working part-time.

Before such a Nakamoto, a beautiful girl who self-proclaimed had come to return the favor, appeared. “I’m the reward for Hero who had defeated Demon King”, said Angelica, a girl who came from another world that persistently tempted Nakamoto to make her his wife. Together with a high school girl who looks like Elsa, his beloved girl that he lost in another world, Nakamoto with his cheats skills got caught in a harem life.

Emperor Zi Yu used 5 strikes of his axe to split mountains and unify everyone underneath the heavens. He partitioned the land into 9 areas, thus establishing the Nine Cauldrons which eventually became known as the 9 prefectures.

Zhou Wenwen, who had traveled to a parallel world because of sudden death, thought that he could only live in such an ordinary life in this life, but the golden finger finally opened. He has a store where he can buy technological items and magic equipment to ensure his survival.

But the threat that followed made him realize that this place is not ordinary, because there are Transformers, Marvel, the Dark Portal from World of Warcraft, etc.

- Description from novelbuddy