One Piece - I Am A Different Luffy! - Chapter 498 - 496 - The future of Lulusia.

Sometimes, as we go about with our lives, we all happen to think of one specific thought at least once.

In the foreign world, the martial artists dominate the world and the sword of the emperor controls the fate of hundreds of millions of lives! Long Yu, the number one killer on Earth, after dying, takes rebirth in this new world in an aristocratic family of martial artists but faces rejection because he is unable to practice martial arts.

- Description from Novelupdates

After losing his parents in a car accident, Ryan immediately caught his fiancee cheating on him with his best friend. In just a few days, he lost everything he loved, so Ryan decided to buy a house in the mountains to process all those events. However, something happened before he could even enter his new home: the end of the world. Monsters began to appear out of nowhere, and dragons began to dominate the skies. After losing everything, Ryan, who had lost his sense of reality, found new goals with the world in that state: survive and get stronger. Dungeons, classes, monsters, skills, the chance to obtain the DNA of other monsters... Ryan was decided to use them all because he no longer would become a spectator in his own life. Maybe with power, he won’t lose anything anymore. The story, all names, characters, and incidents portrayed in this production are fictitious. No identification with actual persons (living or deceased), places, buildings, and products is intended or should be inferred.