I became a god by treasure hunting after arriving 500 years early - Chapter 870 - 581: The Reason for the Death of the Myth of the Monster_2

In a world of endless star fields and interdimensional wars, the wizards' floating city conquered one world after another.At the wizard academy, through blood-stained exams, the towering wizard tower sent wizards batch after batch.Becoming an apprentice wizard, Richard activated the miracle furnace deep within his soul, where constant refining of materials granted him knowledge and skills...The veteran's weapon could be refined into legendary martial arts techniques.The ancient wizard's encrypted notes could be refined into lost knowledge.The remains of brutal monsters could be refined into monster bloodlines.In this era of great voyages in the wizarding world, Richard was destined to become a leader of his time.

Yo, Hi! I’m Frank, I made a deal with a demon to pay me some money for receiving a guest for a few days every week.
I had no idea about what I have done.
On May 1st, Conan ‘the God of Death’ came to my house. I was forced to let him in and we get involved in a criminal case.
On May 8th, Bruce Wayne ‘Batman’ came to me. I was forced to follow him to fight crime.
On May 16th, Hannibal Lecter, The Silence of the Lambs, came to my home. I can only say that I really can’t stand my guests.

- 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.

Su Yang was an average university student in Shanghai when he received a system that allowed him to add points to things. The point system provided him with missions and by clearing them, he would gain points.