Naruto System in One Piece - Chapter 66: The Arrival of the Four Emperors

Collapsed without warning, and upon awakening, he found himself back in his childhood.He thought it was a blessing from above, but unexpectedly, tumultuous changes ensued, shrouded in mystery...

He is high above, the mysterious and terrible King of the Wild. With one glance, he can see people’s romances. He hates women to the extreme, but at his first glance of her, he dotes on her and spoils her.
She is a humble transmigrator, a miracle doctor who doesn’t care for the many handsome men around her. She only wants to become strong, to be worthy of that god-like man. But when she’s finally sure of her feelings, she finds out she’s already been married for years…
……
When wronged：
She uses strength to hit the big handsome iceberg-like man in front of her eyes. “People say that I’m not good enough for you, but it is you who is an old cow eating tender grass!”
A man seizes the main point and laughs like an evildoer. “This husband has to eat the grass to confirm if it is tender or not!” He puts out the red candle……
……
The world says：
The barbarian king has no heart and has no passion.
A pregnant woman very miserably thinks,” If he has no passion, then who is responsible for this big belly?”

- Description from Novelupdates

Elementals, Enhancers, Beast Tamers, Artifact Nurturers – These four pathways define the magical world of Arcanists. But Finn, a former university student from earth, wakes up in a body treading a whole different path…A forbidden path: The path of a Soul Mage.Soul Mages are the ultimate parasites. They lack the ability to use magic themselves, but instead, wield the power to assimilate the mana-saturated souls of the dead.From every Great Arcanist that once lived, to every Calamity Beast, to every Mythic Grade Spirit Artifact… So long as they were dead, they were simply chaotic souls waiting to be claimed.​But this kind of power does not come without cost. Madness, frenzy, mania, innate wills and primal desires of assimilated souls threaten to drive Soul Mages to total corrosion.In this new world, ​Finn finds himself thrown into the deep end, waking up as a Vessel already housing a full Parade of Chaotic Souls. Now, his body is a battlefield. The souls demand immediate payment, stacking Soul Debts that steal his senses, his consciousness, and his very humanity.​But yet… it is this same overwhelming corrosion that causes the ultimate truth and uniqueness of his soul to surface…

I reincarnated as a lizard in a martial arts world.“Roar!”“He’s using the lion’s roar!”“To deflect the Ten-Star Power Plum Blossom Sword Technique! Truly indestructible as they say!”“This is… the Heavenly Demon Overlord Technique! It’s a Heavenly Demon, the Heavenly Demon has appeared!”It seems they’re mistaking me for something else.