I was around J-rock and J-pop fandoms in the early 2000s and I remember there being anon forums where people posted about their encounters with band members. I've seen stuff I'd rather not know about wrt visual kei bands' kinks. Not sure I remember the J-pop side of the fandom having the same thing though. They're probably more discreet about it since pop idols tend to have that fantasy aspect to them and how they're not allowed to date.

From what I've seen, K-pop fandom is bigger and more intense than what I'm familiar with. In light of the recent sex scandals, I guess some women were indeed harmed and coerced.