Crashing into an Old Flame - Chapter 1: Los Angeles, it is

Vergil, a 21-year-old young man, leads an apparently simple life in a somewhat troubled world. His family is also simple—although his father is no longer alive, his mother has always been by his side, despite being a bit... aggressive. But that's not so unusual nowadays, right?Everything changes drastically when Vergil, after an unexpected death, awakens as a demon. To his surprise, he discovers that he has accidentally married beautiful Pure-Blood demonesses.Now, he will discover how the world really works from a Demon's perspective.

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

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Raised by a league of assassins and trained for thirteen years, Shan Yue was seventeen when she took the throne of best assassin, becoming an untouchable legend amongst assassins.

Despite being legendary, she put her faith in the wrong people and was killed by her own league’s betrayal. However, while Shan Yue thought her death was assured in the violent explosion, she was surprised to find herself reincarnating into the body of a useless female student.

Forget how pudgy and dim-witted she was — she seemed to get into fights every day! Her original body’s sister sneered, “Fatso! All you do is eat… and look at how ugly you are! You really embarrass me!”

Fat? Ugly! Shan Yue started a daily training regiment, rapidly slimming down and becoming a ravishing beauty! Her original body’s mother snapped at her, “How did I give birth to a child as stupid as you?! Always last place in school — you embarrass me!

I should have strangled you right after I gave birth to you!” Stupid?

Last place in school? Shan Yue lifted a finger, and the principal of the top school in the capital personally visited, offering a transfer to his school. Elite hackers, doctors, mercenaries, math geniuses…

All of them were now vying for her attention! Though she managed to get the chance to become normal after going through so much, she accidentally become a big shot again, even finding herself a two-faced bigwig for a husband! Shan Yue: I just wanted a quiet life, but my abilities prevent that. Sigh…