They call them junior idols. It isn't hardcore but it's as close to hardcore as you can get without crossing over that line. I saw some of it for sale in Seoul and a couple of other cities in Korea.

The videos almost always consist of the girls posing in sexy or minimal costumes, swimwear or lingerie. One of the Koreans who worked for me showed me one of an 11 or 12-year old girl in a very small thong bikini getting a full body oil massage from an adult woman.

Koreans and Japanese share the same kinks. I don't know why they hate each other so much.