Naruto System in One Piece - Chapter 480: Formation Technique

"In her previous life, she is used by her first love to send her own company into the tiger's den. She becomes bankrupt, gets kicked out of the house by her father, and becomes the target of ridicule by the family. Worst of all, she believes her best friend's lies, thinking that everything was done by her ‘husband’. Under her best friend's ploys, she almost kills him and is ultimately sentenced to prison, where she dies of depression.

Reincarnated as a baby who was in his mother’s womb for a hundred years, the moment Lin Xuan was born, the whole world was shocked.

It was the Great Age of Pirates, surging forward with their thousand sails unfurled.

One young man from earth ate the Goro Goro no Mi (Rumble-Rumble Fruit) and joined the Marine.

Justice vs Evil, Freedom vs Tyranny, the colliding waves between them would never cease.

But all of this…..”I couldn’t care less about!!”

At the summit of the war, surrounded by ten thousand people, Rowen held a thunder halberd in hand and walked forward with strong steps.

Rivals meet face to face, but only one could become the King.

Wu Lai was an ordinary high school student. One day he was struck by a flash of lightning from a different world, and suddenly entered a fantastic world full of magic and swords. Since then, he started a totally new life. In this supernatural world, he had his ups and downs, experienced numerous battles, subdued powerful evil beasts, and fell in love with a belle. His nickname “Demon King” was remembered throughout the ages there.

Stay or return was a question. In the face of this choice, Wu Lai, with the nostalgia and gratefulness for the original world, finally chose to stay…

Here was the legend of “Demon King”…

- Description from Novelupdates