New Age Of Summoners - Chapter 2007 - 100 Divine Body Cultivators takes charge

The elf girl, Aria is an adventurer. Her enchanting, lovely features attracts everyone. Her twin peaks are ripened to the point of exploding. Then, being embraced in between those twin peaks was a little animal… his name is Tama.

He looks like to be a cat at first glance, but Aria and her surrounding companions failed to take notice of single detail. Tama, he’s a human who’d reincarnated, given a second chance at life. His true form, it’s not that of an ordinary cat. Instead, he’s a monster of the strongest class, an extremely young behemoth.

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

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.