The supporting character's harem is very normal - Chapter 7: F rank talent…

Lin Chen was persecuted by his childhood sweetheart and accidentally obtained an ancient legacy. From then on, he embarked on a path against the heavens!“I am a sovereign! Those who insult me will be killed, those who obstruct me will die!”

After his girlfriend broke up with him, wandering all over the place, Xia Tian happens to see a girl about to be hit, after he saves her, he ends on the hospital. Now thanks to his accident Xia Tian awakened the ability to see through anything, be it weak points, or through clothing, nothing escapes his eye. Especially girls.

- Description from novelupdates

Wang Yi gets a key, opening a door in 2022 will lead to 1982, and opening a door in 1982 will return to 2022.

Two very different great eras appeared before him:

Abundant dietary protection, developed industrial products, miraculous medicines, and explosive information, this is 2022.

Simple folk customs, rich wild resources, scattered antiques, and treasures of the age, this is 1982.

Traveling between these two eras, Wang Yi didn’t think much of it, he just wanted to live a good life.

- Description from novelbuddy

[Have you become more learned today?][Accounting for the capacity of your brain, your study efficiency has been increased to 28 times that of normal.][The remaining amount of energy you have for studying today, 26 hours.][You will enter an exhausted state when your energy is depleted and be unable to obtain new information.][Please relax by using the functions within the system and restore your energy as soon as possible.]With limited energy and the onset of fatigue, the Study Monster had no time to think too much--papers to come!Had the heavens not grant me this system, the unending sea of knowledge would seem like a long night.