I’m The Only Granddaughter Of The Strongest Duke

“There’s no way a sword made by Mr. Royce could be this awful—!”
My business sabotage was a total success.
But I couldn't stop there.
I spoke politely to the heroes who had come looking for my father.
“Null Royce? I don’t know anyone by that name. I only live with my mom.”
Sorry, Dad.
My plan was a perfect success.
My dad’s weapon shop was completely deserted, and not a single hero came to commission a sword from him.
I thought all that was left was for the two of us to live happily ever after, but…
“You… child, how old are you this year?”
The strongest Duke in the Empire is suddenly claiming that I’m his granddaughter.
What on earth is going on?
What exactly is happening to me?