I Accidentally Seduced the Male Lead's Younger Brother

She possessed the mistress of the male lead in an R19 novel.
In the original novel, the male lead was a tr*sh who abandoned her after getting her pregnant, saying that he belatedly realized that he loved the heroine.
Fortunately, it was still before the original work started.
I decided to scrap this sh*t by myself.
***
“No, I don’t want to.”
I flatly rejected Killian’s offer to have an affair with him. When he asked me why, I smiled brightly and answered.
“The Young Master is not my taste. If I must say, your younger brother is much preferable.”
“What? You prefer my younger brother?”
Yeah. Not you, but your brother.
***
Unlike the original, I firmly set up an iron wall, took care of Lexion, the younger brother who was abused by his older sibling, and protected the original female lead who has low-esteem against that shitty male lead.
And now that I’ve already done what I have to do, I’m off to go.
But a few years later,
Lexion, who pushed his older brother and sat in the Duke’s seat, came back to me as a beast with a decadent beauty.
On top of that, he’s even holding the engagement document that I signed as a joke during childhood.
“I’ve never forgotten you for a moment. Please marry me, noona.”
No, wasn’t that just for playing house?
Everytime I refuse his marriage proposal, he will gently hug me around my waist, and ask in such a cold voice.
“Did your taste change while I was away?”
Lexion’s eyes were full of life as he asked.
It’s as if when he found out who my type was, he’ll kill it right away.