The supporting character's harem is very normal - Chapter 87 Ryne – Mom?

Learning crude martial arts had always made Fourth Miss Zhu the laughingstock of Beijing’s elite families. In their eyes, such skills were fit only for common bodyguards.Yet Zhu Changle, who considered herself invincible, felt no shame. On the contrary, she took pride in her abilities.Not everyone could protect their own household, but she could! And exceptionally well at that! She’d even dare to turn the whole of Beijing upside down for the sake of her family’s estate!Don’t believe it? Just try her!

As a walk-on, he had been the mistress of his sugar daddy for three year. However, they only had met each other for a few times.
As a boss, his sugar daddy had tons of lovers.
The walk-on: The cake shop is the only thing I love in this world. Lovers? Never want one.
The boss: No problem. Nobody wants that.
Then, they fell in love with each other…
Shameless playboy x heartless rogue
1v1, this is not a decent love novel.

- Description from Novelupdates

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

Ding!『You have acquired the skill: [Universal Language] – All tongues shall now bend to your understanding.』『You have acquired the skill: [Dimensional Exchange] 』『Item Detected: [Gold Coin x50] 』Initiating Currency Exchange…Exchange Rate: 1 Gold Coin = $1,000 USDConverting [50 Gold Coins] → [$50,000 USD].....Kael Lancaster grew up believing his family was ordinary—until he discovered that his estranged grandfather, Theodore, was a multi billionaire.Struggling with his family's debts and uncertain future, Kael decides to approach his grandfather and move into the Lancaster estate, becoming the old man's caretaker. For two years, he endures the family's contempt and Theodore's cold indifference, clinging to the hope that his loyalty will one day be rewarded.But when Theodore dies, the will delivers a brutal blow: Kael inherits nothing.Or so it seems.However, His grandfather had left him something else.A portal through which he could travel to another world—Kael can trade between worlds, amassing power beyond imagination.