Kujibiki Tokushou: Musou Hāremu ken - Chapter 218

He Lang died by his own hands for the sake of his imperial younger brother’s ambition, whom he loved. He was offered to be reborn in exchange for giving up his past romantic feelings. Reborn without the burden of his romantic feelings, he brings with him a manual to new worlds. He wholeheartedly followed the instructions of the manual to complete the tasks, not knowing that the originally slag gong was blackening…
He pleaded to his affectionate Emperor brother to release him, he pleaded to the paranoid prisoner next door, but until the end he remained baffled.
In the end, he discovered that the full name of the manual was – “Slag Shou Cultivating Manual”
Σ (っ ° ° °;) っ!

- Description from Novelupdates

Adrian Voss was a forgotten beta tester—erased by a corrupt game company that put profit over players.Now reborn in Primordial Abyss with a glitched class that lets him control dungeon bosses, he doesn’t grind levels… he grinds players.Every monster he subjugates becomes a weapon. Every raid boss he enslaves earns him passive income. And every overconfident guild that steps into his domain?They drop loot when they die.But this isn't just another OP power trip. Adrian doesn't win because he's stronger—he wins because he's smarter. He lays traps like a raid leader, exploits mechanics like a dev, and rewrites the system from the shadows.From dungeons to PvP, he turns the most advanced gaming system ever built into a weapon that stabs its creators in the back.Now the streamer assassins, sponsored guilds, and even the developers are hunting for the one they call...The Dungeon Phantom.Too bad they don’t realize:The real dungeon isn’t the game.It’s the one they’re walking into.Let the hunt begin.

An AI calling itself Schema has assimilated earth into its system. As a consequence, everyone gained access to status screens, power-ups, and skills. This AI turned these concepts from fiction to fact. It's easy to become intoxicated with leveling up and becoming stronger. To some, it's too good to be true like living out a dream.

For Daniel, however, it's closer to a nightmare.

He's in a bit of a predicament. Cracks in our dimensional fabric have unleashed terrifying beasts from dark, abyssal places. Schema organizes these cracks into dungeons, giving the native species of the planet a chance to fight back. Daniel finds himself trapped in one of these dungeons. Not long after, he discovers there's only one way out.