Lilliny I think the Emperor thing was a twist, so there's a real evil villain who killed Nana's family - it's a pretty common trope in romance stories - you hate the love interest for "killing" your family, you fall for him anyway, and then surprise! Turns out he didn't kill your family, after all! There's a real evil mastermind behind it. Take revenge on him/her, and then live happily ever after with your love interest guilt-free and no longer needing to antagonize over "sleeping with the enemy".
Gem4Life Well...yeah. It happens. I've seen it happen a lot.