>>49201610NTA but while it’s not really related, I think that speaks more in terms to Japanese tastes than anything. Like there was one geisha/prostitute called Sada Abe who killed her lover by strangulation and then cut off his dick and balls and shoved it in her. This case was so popular at the time that people couldn’t get enough of it, with multiple false sightings being claimed of her and it would go on to inspire eroguro in a sense.
I think Japan’s fascination with these kinds of disturbing elements is mostly tied to their culture because of it, and with the economic boom during the 80s, I think that just resulted in so much weird stuff being made or distributed just because they could.