Who knows. Could be simulated but they do have pixelation here and there. I have a few of these, I think it might be simulated but that doesn't stop me from enjoying these sexy ladies.
Remember the OP: What I mean is Japanese produced AV with Korean girls (like a sub genre), not Korean XXX
EDIT: If it isn't simulated maybe they use the tactic of just not filming anything they would have to mosaic out later anyway?
lol Barrel is a pretty popular Korean swimwear/etc brand that former K-pop singer/model (and total hottie) NS Yoon-G models for, imagine they're not too thrilled to be on a JAV cover.