"At that time... I wasn't aware of Lady Eustace's behavior toward you" is the most bullshit sentence I've ever heard. You have TEN YEARS worth of engagement, and you tell her that you didn't realize, or at least hear that something wrong had been going on? The fuck are you doing all that time, mate?
Anyway, I hope there are more manhwa/manga that has this type of plot. I only know two manhwas, including this one.