The supporting character's harem is very normal - Chapter 9: Going to the Karol Empire?

The one single goal in life of the Strongest Old Sage is to subjugate the Demon King. In an epic final battle, both of them met their mutual destruction at each other’s hands.

However, the Demon King was not completely destroyed!

In order to destroy the Demon King once and for all; post-death, the Old Sage trains in the World of Gods and reincarnates as the Apostle of the Gods, Will.

In the reincarnated future, the Old Sage had become a legend and his former disciples hold the supreme authority in the world. The disciples had created an organization to oppose the Demon King and an academy to nurture the new generation of Heroes.

Thus the Apostle of the Gods, Will (8 year old), enrols into that Academy of Heroes.

This is the story of a boy on a mission to save the world through epic battles while enjoying Academy life.

A teen is summoned to another world as the Hero. It turns out the Hero can power up women with his cum.

There is a kind of person in the world who is indifferent, cool, arrogant, and especially a bit petty. There is also a kind of person who is lazy, gentle, considerate, and even adeptly flirts with girls. When the male god completed a shocking 360 transformation from the former to the latter, Tang Xia’s first reaction was…is this a fantasy world?

- Description from Novelupdates

The Great Yan Empire exists in a world where respect can only be earned through strength. Within this Great Yan Empire, the four great clans have always stood above the rest. Among them, a particular incident in the Lin Clan resulted in the banishment of a certain individual who went on to start his own family, in hopes of one day being recognized again by the Lin Clan, and rejoining them...

Hailing from a banished family of the Great Lin Clan, when Lin Dong was very young, he watched, powerless, as his talented father was easily crushed and crippled by the overwhelming genius of the great Lin Clan, Lin Langtian.

With a despairing father, a heartbroken grandfather, and a suffering family, ever since that fateful day, Lin Dong has been driven by a deep purpose; to take revenge on the man who had taken everything and more from his family.

Armed with nothing but willpower and determination, join Lin Dong as he unknowingly discovers a destiny greater than he could ever hope to imagine when he stumbles upon a mysterious stone talisman...