The supporting character's harem is very normal - Chapter 521: I will confront the Pope

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

Village doctor Zhang Xiaoshan attained a variety of Divine Skills.Mind-reading, treasure appraisal, and miraculous healing, he became capable of everything.

Chen Sansi traveled back to the chaotic end of a dynasty, thankfully with the hardworking system by his side. He originally wanted to hunt to earn money and someday go to the Martial Arts Hall to learn some basic fist and foot techniques, aspiring just to be an ordinary rich man. Yet, fate had other plans. With officials imposing heavy taxes and the Martial Arts Hall bullying the citizens, he had no choice but to enlist in the army to survive, becoming an archer. From “archery (entry-level),” he worked tirelessly up to “operating a ten thousand weight bow, where arrows cannot be dodged,” taking the heads of enemy generals from a hundred miles away! From “basic soldier’s spear technique,” he worked tirelessly up to “National Guardian Dragon Spear, growing more valiant with each battle,” standing firm with a spear on horseback, alone turning back the Enemy Army of a million! Years later, Chen Sansi, having campaigned in the south and battled in the north, was truly invincible under the heavens, commanding two hundred thousand of the Iron Cavalry. Watching his subordinates forcibly ascend him to the throne and become emperor, he felt quite helpless: ’You... you have really caused me trouble!’

Traversing into another world, Zhang Xuan finds himself becoming an honorable teacher.

Along with his transcension, a mysterious library appears in his mind.

As long as it is something he has seen, regardless of whether it is a human or an object, a book on its weaknesses will be automatically compiled in the library.

Thus, he becomes formidable.

“Emperor Zhuoyang, why do you detest wearing your underwear so much? As an emperor, can’t you pay a little more attention to your image?”

“Fairy Linglong, you can always look for me if you find yourself unable to sleep at night. I am skilled in lullabies!”

“And you, Demon Lord Qiankun! Can you cut down on the garlic? Are you trying to kill me with that stench?”

This is an incredible story about teachers and students, grooming and guiding the greatest experts in the world!

- Description from Novelupdates