Krystal Swift reminds me of Sandra Star. The two look nothing alike (other than the fact that they're both blondes) and Krystal is Czech while Sandra is German. But they both have this thing about them, and I'm going to try to explain.
I don't think Krystal and Sandra look sweet and innocent. I think they look sweet and sexy, so that's not it. But they both have a look that would make the average person say, "There's no way these girls would have sex on-camera." But they do, and what's even better about that is that they both really enjoy themselves. Both Krystal and Sandra smile when they're sucking cock and fucking.
Okay, I got it: Krystal and Sandra don't fuck like porn stars. They fuck like girlfriends or the girl you just took out on a date who's seen a lot of porn and wants to fuck like a porn star. And they succeed.