How is This Hot Duke Just a Background Character?!

I was reborn… as a background character in a romance game?! And my fiancé is a hot duke?!
Reincarnated as 'Leticia', a background character in a game, I found out that my twin sister, who has a horrible personality, pawned her fiancé, Lionel, off on me. When I first met Lionel, he was just as chubby as I'd heard… But I soon realized he was a diamond in the rough and decided to make him shine!
But that's when I discovered that my newly hot fiancé is acting like he's head over heels for me…!