MTL - Pirate: I Shock the World From the Top - Chapter 42

As the last abyssal demon in the world, Wen Long was pulled into various worlds to do tasks by a guy who claimed to be a system. The goal of her mission was to save those villains who had been blackened for various reasons…

- Description from Novelupdates

The moment I received the restructuring notice from my company, the world changed with a deafening roar, as if the sky was collapsing.[The sale of this Earth has been decided.][Restructuring of personnel will be carried out.]A life-or-death restructuring. Missions that grant special powers upon completion. If this is some miraculous prank, I’ll give it my all!“I found it. A way for us all to survive.”The meteoric rise of Lee Eunho, the restructuring target, begins now!

I exist in the darkness, disappear under the bright light, and will eventually devour the sun and turn into the shadow of all things… Known by people as the indescribable terror of darkness; the king of shadows; the dark day; the existence of the shadow of the world , is still just a somewhat special high school student, facing a weird death game…

- Description from novelbuddy

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.