
They aren't direct cousins though, they are distantly related. And honestly, I'm sure a lot of people have distant cousins they aren't even aware of. Meaning it's far enough not to be considered incest, even for cultures that don't condone first cousin marriages.
Anyway, plenty of cultures have their own views on what constitutes incestuous relations or not. For some, marrying within your own clan, even if you have no blood relation, is considered incest.
Sorry if it seems like I'm personally directing this at you, I'm not. I'm just a little tired of people saying "ew cousin love is incest" because really, we should respect other peoples' cultures.
Though I still don't think cousin relationships apply here because Carol and Senpai, are again, distantly related. Senpai says Carol is the daughter of a distant relative, so they might not even be distant cousins but something else entirely.

Yeah I thought they looked similar too. Though I feel like it's probably because they are both European (I think). Carol is fully European from her Dad and Mom. And I assume Misaki is half, I forget if they ever mentioned this, but considering his name I'm gonna go with that.
Also this is a manga, so all European people will just be blond with light eyes, hence the similarity. It's still possible the two barely share the same blood.
And based on genetics, their kids wouldn't have any kind of deformities at all because of how different they are. I mean, I bet it's like a 1% similarity. Or 99% because apparently all humans share 99% of DNA. lollllllll
Anyway I shouldn't be applying too much of this data or whatever on manga characters. Sorry I went off topic. I was just thinking about this for a while. Now I want to see Misaki Senpai's parents...O_O
I'm not a big fan of Carol loving her first cousin, cause you know insect. But I do know people in real life who are half brother and sister and are married and have 3 kids...... nice people and kids are fine but still grosses me out. It's a genetic thing.