It is refers to a manga about a girl the tragic changing from shy nerd to a promiscuous. It’s a disturbing transformation of a nerdy, shy, wallflower girl into a mentally scarred but extroverted, ragingly promiscuous delinquent. This manga is pretty far beyond what many people can normally tolerate, and, indeed, can either badly disturb them. Those who have never seen this horror ignore the number and avoid the manga.
If you’d like to get a quick snapshot of the kinds of things that are on this manga, get in to the YouTube videos and see what videos have surfaced about it. This all became a thing in the Meme in Reddit and then all the trolls were all over.
The story ends really, really badly. People had distaste with it so much that they started to make alternate-reality-versions to patch things up. The manga seems to have been around for well over 5 years, mostly in the south Asian region that has seen it boosted by some YouTube videos in recent years.