Responses
I'm pretty sure I have that chapter bookmarked (like 40ish)? It's actually unclear if they're in the underworld or not. It started in her world because she was walking away from the human who was crushing on her. The blue eyed, silver haired demon tried to kidnap her, but they were in her world. Lux teleported her away, but it just looks like general...barren area? It was a hot couple of chapters, but I don't think they were in the underworld together. (Plus with it being so unsafe, I don't think Lux would take her there willingly.)
This ain't the first time they fuck in the underworld y'all they did it in the early chapters too when lux went off all demony. You guys just can't handle the freak levels