Just made an account because I was curious about a site I found through a youtube video.
The channel who covered the site is called "Star Island", and I suggest you check our their content if you're interested in japanese websites and screamers.
Link to the video:https://www.youtube.com/watch?v=_xXJwZ5vgto
Link to Star Islands channel: https://www.youtube.com/channel/UCcO6BOPrvZ72iFxptHxovzQ
The site in question is called えんじぇるぱーく武蔵 , which would translate into "Angel Park Military".
It seems to be an artistic website however it includes screamers, NSFW, flashing images, loud sounds and (from what I've seen so far) cartoon gore. The site is in japanese and seems to have been active since 2013. They have their own soundcloud page and possible blog posts, but I'm not entirely sure.
Link to the site (WARNING, there are many flashing images and bright colors on this site so I don't reccomend you click on it if you are prone to seizures.): http://um6bit.kikirara.jp/
I haven't dug too deep and since I'm not fluent in Japanese I don't understand much of the site. I'd love to hear your thoughts! (Note: I'm pretty sure the site doesn't have any viruses since my computer is fine after scrolling through it, but I'd advise you to be careful before you click any links.)