My Ex-fiancée Has Had Enough of My Cute Little Sister

I, Charlotte, the daughter of a count who was raised strictly by my parents to be able to do everything, became engaged to Leinhardt, the legitimate son of a duke.
My sister Milim cries that it is not fair. She claims that I am the reason why she is sick.
Leanhardt, who had long been infatuated with her sister’s reputed fairy-like beauty, abandoned me so easily when he heard the story.
“Your sister is more beautiful than anyone, but I knew you’d be better.”
Soon after, Leanhardt came to try to get back together with me.
No, it’s too late for that since I’m already going to marry the crown prince of a neighboring country.
I’m grateful to my parents for giving me a strict education in a wide range of ancient and modern knowledge, as well as languages.
For some reason, my sister was spoiled like a child and had no education or anything. She grew up to be selfish.