Naruto System in One Piece - Chapter 348

A polite and lethargic boy was reincarnated in another world as a vampire bishoujo.

Traveling through the era of national beasts, Su Yi discovered that his pet beasts could actually choose a special evolutionary route!

When others are still trying to make the red fox evolve into a flaming fox, his nine-tailed fox fairy has already fallen in love with Liaozhai;

When others are still trying to make the thorn grass evolve into a thorn tree, his queen of thorns has already suffered from secondary school;

…

Looking at these strange beasts, Su Yi fell into contemplation.

Will I still be a beastmaster in the future?

This is the demon!

- Description from novelbuddy

“World conquest was never part of the plan.”Yu Chen was just an ordinary programmer, slaving away at his desk, fixing bugs for a popular kingdom-building game.His life was a cycle of endless work, sleepless nights, and little appreciation. One fateful night, while struggling to fix a game-breaking bug that granted players an absurd amount of upgrade points, his exhausted heart gave out.But death wasn't the end for Yu Chen. He awoke in a world strangly familiar... he had transmigrated into the very game he had been working on, now inhabiting the body of a notorious tyrant emperor, Arkanos Bloodbane, whose empire was on the brink of destruction.Surrounded by enemies, with rebellions simmering within and war on every front, Yu Chen, now Arkanos, quickly realizes the gravity of his situation.But to his shock, he discovers that he still has access to the game's system interface—complete with the million upgrade points from the bug he had tried to fix!With his knowledge of game mechanics, strategic mind, and a wealth of upgrade points, Arkanos sets out to turn the crumbling empire into an unstoppable force. He begins by summoning legendary heroes, deploying advanced technologies never before seen in this world, and revolutionizing his military and infrastructure.As he pushes his empire to greatness, Arkanos must navigate the treacherous politics of the imperial court, fend off treacherous factions, and outmaneuver the rival nations that seek to destroy him. But with each victory, he realizes that this world is not just a game—it's his new reality. The stakes are higher, the dangers more real, and the consequences of failure more dire than ever.[Reminder, contented intended for mature audiences.]

Xu Jun finally defeated the BOSS–the Dark Demon King, in this stand-alone, virtual reality game. When he wanted to go out to browse Weibo and express his mood, he suddenly encountered a game BUG and immediately passes over to the game world.

He became the man who finally took down the Great Demon King in this world. Gratifying! The attention of millions of people!

……However, he did not know the development of this world was not the same as the game, the Demon King did not die, rather his soul entered into Xu Jun’s body; this Demon King knows of all the stupid things Xu Jun does everyday…….

- Description from Novelupdates