I’m Trying to Become the Dark Duke’s Family.

I reincarnated into a book—into a terminally ill body with the same rare disease as the female lead.
In the original story, the mastermind villain finds the cure for her…
But the novel hasn’t even started yet.
If I wait until then, I’ll die.
So Rowina decides to snap the mastermind out of his broken, listless life and push him to obtain the cure ahead of schedule.
Which is why—
“Hello, Duke. I’m from the Townsend Orphanage. My name is Rowina Whitfield, and I’m ten years old.”
“…What?”
“If you make me part of your family, then whenever you come home, I’ll run out to the front door and welcome you.”
“What on earth—”
“And, um… this is me really working up the courage to say it.”
“What now?”
“I’ll even give you a goodnight kiss before bed.”
I decided to become part of the mastermind’s family.
With the mastermind’s sponsorship, I safely obtained the position of heir.
Once I found the cure, I planned to hand the heir position over to my fiancé and then leave.
That was all I needed to do.
But then… why?
“You said you liked me best. Why are you changing your tune now? Have you decided you don’t need someone like me anymore?”
“Child, if you hate that boy, how about becoming my adopted daughter? I’ll give you all my wealth.”
This family… likes me way too much…?
And on top of that—
“You said you’d take responsibility for me, Rowina. And now you’re going to leave me?”
…What is his problem now?
“You said you wouldn’t betray me. You said you were on my side.”
Why do these people love someone like me, who has nothing?
And maybe… do I get to be greedy for love, too?