The Achievement Junkie - Chapter 41 A Hidden Tomb?

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

I didn’t know this was a world inside a game. And I didn’t know my master was a mid-boss. “No way… wasn’t she supposed to self-destruct because of her personality?!” …I’m sorry.

Wu Tao, a small mysterious trader, suddenly appears in the city of Jinan and encounters with Yuanbao, a foxy little beggar. Wu Taos identity as a trader is suspected soon, because on the day before he appears, Sun Jicheng, a millionare in Jinan dies a mysterious death, and people finds the dead one is his substitute. Around the countless wealth, confusing identity and the seven mysterious stars in the little beggar, various figures come on stage, starting a magical adventure story.

An Individual from Earth finds themselves in the Shinobi World, equipped with a Scientific System. From that moment, he delved into scientific research far ahead of its time.