Isekai'd as a side character

I was given slime as a gift from my war-crazy brother.
At first, I decided to keep it under the bed and raise it secretly, but I grew to befriend it. I would talk to if day with all kinds of secrets to my first-time friend.
Everything from the fact that I am the possessor to the content of the original.
“The male protagonist, Alexey, was amazing.”
At my words, the slime’s blue body glowed red.
○ /
○ : domestic abuse; child abuse

The female lead, Nanelia, is warned by her sister that their evil, abusive step-mother is going tto marry her off to a man more than twice her age. After escaping, Nanelia finds her prince and lives happily ever after. But aren’t we forgetting someone?
What’s do be done when our protagonist is transmigrated as that little sister who was left behind?
○
○ : child abuse
○ Takes place post-story (I’ll allow it lol)

I’ve transmigrated into the body of the wife of the mad villain emperor in an angsty novel How will I escape? By running away quietly when the main character appears. This love-blind emperor won’t even remember that I exist once he lays eyes on her I really didn’t do anything. But the villain emperor has asked me to return to the palace with him, and not the her.
○

Yoo Jung-in dies in a car accident and wakes up as Rosé, a maid from a novel who was locked in a tower with a prince and violated him. The moment the prince leaves the tower, he kills her.
“No skinship without consent, no killing the maid after leaving the tower.”
She thought they had made a satisfactory deal…
○
○ : rape (OG Rosé rapes ML but Jung-in transmigrates before it’s happened; OG Rosé had still forced ML to kiss her)

One day, I awoke as Lindsay, the twin sister of my favorite terminally ill female lead, Lique. To prevent the female lead’s death, I will marry the infamous Prince Hernán in her stead.
○

After being hit by the fateful truck of transmigration, Jeong Yujin wakes up in the world of a fantasy novel as Lord Eugene Linweisen. Eugene’s main role may be to marry the story’s antagonist, Grand Duke Ivilaron, but Yujin has an even bigger job to fulfill: saving the world.
○

Ning Yi, a modern-day doctor, traverses into the universe of a novel and becomes a vicious supporting character who dies in the story. Forced by a system that ensures she acts in accordance with the story to her death, Ning Yi finds that only by getting near Prince Ning, the villain of the novel, will she be able to escape the monitoring of the system.
○

I was envious of the extra that picks up money more easily than the heroine of hardship, and one day I was imagining becoming wealthy while looking at the land that would increase in value.
Eliana, a loyal extra maid of the Countess heroine. Now all she has to do is become rich in her land, and even her villainous peacock duke, who she gazed upon her mountainous land, begins to follow her.
○

Duke Adler, referred to as the greatest man of the Asgard Empire, is as handsome as a sculpture. However, he is also a serial killer, playing the role of the villain in a novel. On top of that, Princess Charlotte, who was politically married to him, was fated to be murdered on their first night together.
The predicament is that I am the princess fated to die at his hands on that night.
○

She was introduced as a supporting character in a novel who died after giving birth to the male lead’s child.
“I will never have a male lead’s child!”
When I realized this, I was already about to get married.
○
○ : mentions of child abandonment, alcoholism, suicidal behavior, and maternal death