@inoru_no_hoshi v
Conclusion: at least some skz members know enough about kink practices to do them responsibly and well.
Side note: look for the behind-the-scenes videos from Red Lights making-of. Bang Chan & Hyunjin say & do some interesting things.
(I'm at work right now & can't provide links. But feel free to bother me about it in a few hours & I can dig them up.)