Kujibiki Tokushou: Musou Hāremu ken - Chapter 3

An ordinary student, a wretched peeper, a cowardly teenager with a kind heart. In a terrorist attack, he inherited the knowledge of countless elites, embarked on a path of God Jagged Tu…

He is an artist!

He is a mathematician!

He is a psychology Doctor!

He is a master of fighting!

In fact, he is a man

Taken off raw site:

A wretched, dirty young man is working during the summer when he was caught up in a mysterious explosion. After that explosion, the young man is then left with the memories and knowledge of dozens of the world’s experts.

He has changed, his heart has become cold, iron-blooded. He became a killing machine, his mind turned mechanical, calculative. Everything goes according to his plans and calculations!

In this magical, slaughterous world, a door is opened for him…

- Description from Novelupdates

In a world where human and monsters relied on mystical fruits and their inner power to fight for dominance, a lost soul was thrown, given the powers from all the other worlds he’s known. But there was a catch; he had no control over what power he would get! With knowledge beyond that of most, he sails his path to the top of the one piece world!

Original fanfic, not a translation.What happens when a young soul reincarnates a Huo Yuhao from Soul land II.Will he follow the original route where all what awaits him at the end is a collar around the neck?orwill he follow his own route clear of manipulation, exploitation and misery.Join this young soul on his new journey in a familiar and an unfamiliar world.

Birth rates are decreasing. Hope is vanishing. The world has gone gray.Humanity, drifting in quiet collapse, receives an email.Every person on Earth. Simultaneously.The Aegis Mandate.Disguised as a cosmic aptitude test, it triggers The Incident of Separation—a global psychic cataclysm that erases identities, wipes memories, and divides all survivors into three factions: Law, Neutral, and Chaos. Overnight, cities become battlegrounds. Apartments become dungeons. Ordinary people become monsters—or the ones who hunt them.Ragnar Vhagar was just a loner university student. Now, thanks to a system he didn’t ask for, he’s a newly minted Demon King, locked in a crumbling apartment with goblins under his sofa and a glowing soul crystal next to his frozen peas. His new job? Build a deadly domain, defend it from invading “Heroes,” and somehow level up fast enough to not die.Alongside him is Isabelle Thorne, a razor-sharp warrior of few words and one very sharp sword. Their reluctant alliance, born in blood and snark, evolves into trust—and maybe something dangerously close to affection—as they rise together through the layers of the game-like world they’re trapped in.With each conquered domain and defeated boss, Ragnar realizes the truth: the dungeons aren’t meant to crown a winner. They’re meant to break the players. The Law faction wants control. The Chaos faction craves destruction. But Ragnar? He wants something they’re all too afraid to say out loud:Freedom.In the ruins of Kanta’s ogre stronghold, Ragnar and his misfit warband take their biggest step yet—claiming a kingdom, unifying a fractured system, and preparing for what comes next. The Heroes are watching. The gods are stirring. The world is watching a war.And somewhere deep beneath it all... Ragnar is rewriting the rules.