The supporting character's harem is very normal - Chapter 412 Lathel’s decision

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

I was a genius in the Earthen Plane.

Sold by her own grandmother to become a shared wife to the poverty-stricken Ye brothers for twenty taels of silver, Liu Duo, unwilling to succumb to her fate, escaped in the night. She slipped and fell and died an inexplicable death.

After nine years of traveling with her parents, Long Shiyan’s family encountered a group of bandits. Although her parents died, Long Shiyan was able to escape from them with the help of a system. From it, she learned that she was stuck inside the world of a harem novel! In order to revive her parents, Long Shiyan must prevent the protagonist of the original novel, Long Aotian, from capturing wives and attaining a harem. Otherwise, the world would end!

But, after saving a future harem member from Long Aotian’s clutches, why did this girl obtain a more terrifying characteristic than blackening into a villainess…

- Description from Novelupdates