MTL - Princess Medical Doctor - ~ 899 stressed that we do not mix

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

I do not own this imageHe was a swordsman beyond compare—cold, calculating, and relentless. A man who chased power not for glory, but to break the fate forced upon him. Betrayed in his final battle, he died with his blade in hand... only to awaken in a world not his own.Now reborn in the world of High School DxD, Nero carries with him a mysterious System that allows him to defy logic:— Steal and evolve Sacred Gears— Accept world-altering quests— Access a store that sells power itself— And shatter the limits of every universe he entersWith the power of his Void-Forged Blade and a will forged in war, Nero walks among Devils, Angels, and Fallen—but he kneels to none.As he joins Kuoh Academy, crosses paths with Rias Gremory and her peerage, and uncovers the secrets of the multiverse, one thing becomes clear:This world, and every world after it, will tremble beneath his blade.

An 11-year-old boy suddenly woke up,

“...wait, where am I?”

“...I see, so this is the so-called transmigration.”

“hahaha.....hellll yaaaahh.”

“It's my time to show the world who the boss is.”

But he didn't realize what he caused,

“Wait, this isn't what should be... why is he here, and where's that prostitute? And why is my lover with him?”

“Fuck, what the hell is happening here? He shouldn't be here, and that guy should be dead, but how is he alive....urgh,” he grumbled.

“This is MY FUCKING WORLD, why are these guys interfering...aahhhhh,” he shouted.

A transmigrator who thought 'doing good deeds and fighting against evil will make him a hero and ruler of this world' now made a very small mistake which leads to,

“My wife....is a wonderful woman,” the mob character.

“Why? Why? Why? Why......” the mob character rumbled.

“Do you....believe in god?” the mob character questioned with a messed-up expression.

“S-Shall we get m-marry?”

“...” the mob character was shocked.

“I don't know why but I like you, I guess.”

“....” the mob character was too shocked.

“I like you, so be my son-in-law?”

“....” the mob character was too-too shocked.

“How about marrying my daughter and me at the same time?....what do they call that hmmm...'oyakodon,' right?”

'cough, cough.'

“What?” the mob character was finally snapped.

“Big Brother, when will we get married?”

“........”

Transmigrator never expects a certain 'Mob character' and how that 'Mob character' becomes a great disaster for the entire world because of his single mistake.

A/N: This is my first time writing, so give me your honest opinion whether it is good or bad, but please don't be harsh on me... okay, I will try my best.

CHOTTO MATTE....The first five chapters, The Transmigrator will be one to explain everything about this new world. I know I am not introducing the MC suddenly, and it's hard to info dump, but it's just for the first few chapters, so don't be harsh on me.

If you wondered who will be MC then, MC is just a 'Mob Character.'

Additional Tags: Harem, Male MC, Beautiful Female leads, Vampires, Dragons, Elves, dwarfs, Mermaids, Revenge? Deadly Yandere, Incest, Tsundere, Kuudere...Slow-paced

The weak cry out with all their might, yet no one cares; The strong whisper softly, yet their words penetrate deeply into the heart. A Talent Tree ablaze with flames, every leaf bearing different spirit runes, Lu Ye, reduced to a mining slave after his sect was destroyed, used this to become a cultivator and stirred the winds of change in the Nine Provinces...