For k-pop, Japan has notoriously been very tight with licensing restrictions on music. That allowed Korea to leap ahead.
For example: https://news.ycombinator.com/item?id=36016653
If that's the one, it looks like an online manga reading website. There are many of those around. eg mangakatana, reaperscans, mangadex, etc
All other sites you mentioned are fan translations (scanlations).