I Became the Younger Sister of a Regretful Obsessive Male Lead (Pre-serialization)

I’ve transmigrated into the world of the BL webtoon <In The House of Dolls, There’s Another Doll Living There> where I left my one and only spiteful comment. On top of that, I become the adopted younger sister of my favorite character: the obsessive male lead who is later regretful for his actions, but still dies along with the duke in the end. So, I was determined. Since I have transmigrated into this world, I can’t stand by and watch my favorite character die. Additionally, I also don’t want to die. That’s why, author, I'll need to change the tags and the ending of this webtoon slightly! From <Obsessive Male lead> to <Considerate Male Lead>. From <Sad Ending> to <Happy Ending>.

“Brother, please smile like that in front of others as well.” I said to Lucian, who doesn’t smile even a little bit in front of others.
“…”

Was that request too out of the blue?
Lucian looked at me with a peculiar expression.
“If you do that, I will give you a gift.”
I said that because I wanted to help him in anyway I could.

He looked at me for a bit and hesitated before replying, “A gift… Is anything fine?”
“Of course!”
The moment I gave that answer with certainty, his expression changed right at once to that of a starving predator… Did I make mistake?
Then, Lucian calmly replied with an expression full of expectation.

“Give yourself to me, Rachel.”
Huh? What did he say? What did he just ask for?