My System Academy - Chapter 114 The General Mana Theory

When an S-class elite assassin-raised captain of a special ops suicide squad comes home from a high-stakes Africa mission, he finds himself offered something that could potentially set him up for life- a curious assignment that he could use to finally exit his days of war and slaughter.

Then placed into a high-school setting, Lin Yi is tasked by the chairman of a top-tier multi-billion company with bodyguard duty for non-other than his own daughter, a certain little Miss of said high-school.

His enemies, once ranging from drug lords, mafia bosses, political figures, and national leaders, are soon replaced with spoiled kids who happen to have rich papas and mamas, and Lin Yi finds his intense expertise and high-threat skillset misused, and very underwhelmed…

But he does get a harem cast as diverse as his old enemies, so Lin Yi decides that, for the sake of messing around with girls as an invincible entity in a down-leveled environment, leaving his bloody and death-filled war days behind is something he’d definitely want to strive for.

- Description from Novelupdates

A muffled murmur sounded softly,

Crazy goblins ravage the village,

Mutated beasts roam the fields,

The ancient old gods are gradually awakening,

Just when the darkness is about to engulf the entire continent,

A brave man from another world quietly appeared,

This may be the darkest hour before dawn.

Human: “The savior has come?”

Monster: “Have new food arrived?”

Till the fame of the brave spread far and wide,

Walking through every corner of the continent,

He/she/they know,

What is the real darkest hour.

The monsters and humans said in unison:

“I beg you to be human, the ancient gods were so scared that they went back to sleep.”

- Description from novelbuddy

Nate, a transmigrator from Earth, arrived in the anime world of Fairy Tail!He acquired a magic called “Internet!” He developed it and got everyone hooked!You can livestream, chat, and even... hmm? Find girls to date!Sasuga Nate-san, Internet Magic is the best!

At 18, Alex Kain is whisked away to Eryndor, a game-like realm where he gains 'Skill Synthesis', a talent to fuse skills into godlike powers. Battling monsters and conquering dungeons, he builds a harem of strong women drawn to his might and charm. With the power to return to Earth bearing incredible resources, Alex faces a growing threat that endangers both worlds in this epic of adventure, romance, and ambition.