I Accidentally Seduced the Male Lead’s Younger Brother / 실수로 남주의 동생을 꼬셔버렸습니다

Co-production between Moon Pixie and Yeogsa Scantrad - She is the lover of the main character in an R19 novel. In the latter, the latter is a bastard who dumps her after making her pregnant, telling her that he realized too late that he loved heroin. Fortunately, it was before the real problem started.
"I decided to destroy this junk myself."
"No, I don't want it."
I firmly rejected Killian's proposal to have an affair with him. When he asked me why, I smiled and replied that it was not to my liking.
"If I have to tell you, your little brother is much more pleasant."
"And then ? Do you prefer my little brother ?"
"Yes. Indeed."
Unlike the original novel, I took care of Lexion, the younger brother who was mistreated by his older brother, and protected the female leading role that had little regard against the male protagonist. And since I did what I had to do, all I have to do is leave. Yet, a few years later, Lexion, who had succeeded his elder brother and taken the reins of the duchy, came back to me like a fawn imbued with decadent beauty.
To top it off, he held the same warranty document I signed to joke about when we were young.
"I've never forgotten you for a second. Please, marry me."
Every time I rejected his marriage proposal, he would hug me and ask me in such a cold voice.
"Did your tastes change during my absence ?"
Lexion's look said a lot about his interest in me and he expected only one thing: Discover who my type of boy really is.