The supporting character's harem is very normal - Chapter 4: After Lathel’s Death (3)

Su Ran, a music prodigy, woke up transmigrated into a book.

At that point in time, the main story arc in the book had already been completed. As a villainess female supporting character, not only did she need to take over the original owner’s pitiful life in poverty, she also gained an instant son right at his rebellious period.

Ten or so more years from then, the son would turn into a twisted, evil villain. He would appear in one of the extra chapters to pick on the male and female lead’s children.

***

Su Ran: Son, you shouldn’t be too outstanding.
Su Han: Why not?
Su Ran: ’cause you will be killed.

Su Ran: Son, would you like to learn music from me and become a zen, little fairy boy who only needs to drink dew.
Su Han: No, I want to go into business so I can support you.

- Description from Novelupdates

Some people transmigrate into Emperors, others become wangye.

They live in luxury; their hands covering the Heavens.

Some people transmigrate into shizuns, or sect leaders.

They would have the respect of all, their powers supernatural.

Some unlucky souls become villains, but even with their terrible reputations they would still have enough power to summon rain from the sky, maybe even manage to kill off the protagonist.

But Li Changtian, a stand up young man from a good family, who died on the battlefield protecting someone, widened his eyes.

He! Transmigrated!

Into a person everyone wanted dead, with an unabsolvable crime!

Li Changtian: “??? Wait wait, did something go wrong somewhere?”

The magistrate of the Imperial Justice Bureau, Yan Shu, who hated injustice more than anything in the world had just stepped onto his head and said in an ice cold voice: “A life for a life.”

Li Changtian: “&%%%￥&￥#@”

- Description from Novelupdates

Ukei Kaito fought a desperate struggle in order to fulfill his role as a summoned hero. He defeated the Demon Lord and saved the very world, only to meet an end filled but with betrayal. The companions that he’d trusted throughout his journey betrayed him and killed him by sticking a blade through his chest.