Isekai Maou to Shoukan Shoujo no Dorei Majutsu - Volume 10 Chapter 5 part7

The prospective college student Luo Ji, who is enjoying the last summer of the third year of high school, has undergone earth-shaking changes at this moment after accepting the invitation of the game friend and becoming the player of the game of “Civilization Rise”.
This is a war game between the world and the world, and it is a fierce collision between civilization and civilization!
To annex the five continents, sweeping across the three oceans, and see how Luo Ji led his people, in this powerful enemy look around, the battlefield of the heroes to fight for a battle to the most powerful imperial civilization!

- Description from uukanshu translation

One day, Fang Jueyu was called into the study by his parents.Fang Father: “Son, you've turned 20 this year, and it's time to tell you some things!”Fang Jueyu: “What is it? You're not going to suddenly tell me you're a wealthy man, are you?”Fang Father is surprised: “You already know?”Fang Jueyu: “What? Really? I was just saying that.”Fang Father: “However, that's not the point. Today, I am going to pass on our family's heirloom that has been handed down from generation to generation to you!”From then on, Fang Jueyu's life underwent a dramatic change.What? You want to talk to me about antiques and calligraphy paintings? Do you want Wang Xizhi's calligraphy or Zheng Banqiao's paintings? Oh, right, Van Gogh even gifted my great-great-great-grandfather a painting!Why, you ask? Because it was my ancestors who funded their education!You want to talk to me about sports cars? Are you talking about Lamborghini, Ferrari, or the Bugatti Veyron? I hold shares in those companies, and I'm even the largest shareholder!What? Your family owns a mine? Sorry, but many of the gold and diamond mines in Africa are ours too!

Once through the pirates, Lu En became the son of Monkey d Dragon, a grandfather named Monkey d Karp, and an unreliable and neurotic younger brother named Luffy.

Fortunately, the ghost back system is activated!

The completion of the ghost back is 10%, and the training effect is increased by 100 times!

The completion of the ghost back is 20%, and the training effect is increased by 1000 times!

…

One day, Lu En, a ghost-backed master, appeared in front of Luffy who was shouting to go to sea, and made Luffy cry on the spot.

Luffy: “The pirates in the sea are all monsters like my brother? I don’t want to go out to sea!”

Garp: “For a long time, the two boys, Long and Luffy, with small arms and calves, I really doubt that they are not my sons and grandsons. Like Lu En, they are the grandsons of the old man!”

Warring States: “The strongest creature in the sea, land and air is Kaido? No, it’s Lu En!”

- Description from novelbuddy

…but it seems pretty doable.