MTL - Ultimate Assassin System - Chapter 9 Angry Down

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

She and the blind date met man get married soon. She did not expect that the "ordinary" new husband turned out to be the CEO of the company she worked for.

First World : CampioneCurrent - Second World: High School DxDThird World: ???Reincarnated into the world of Campione! Haru Kasugano, our hero slays gods and ascends as the mightiest Godslayer. He battles powerful God-Kings and Campiones, claiming victory after victory. Whatever it is. [Wealth, Power, Beauty] he has it All. Watch him grow stronger as he travels into new realms like High School DxD and the Fateverse, leaving a trail of defeated gods and captivated hearts in his wake.