It's a doujinshi. Fanfiction. I'm a bit bothered at the "sequel" part tho when it seems to be 1. A different timeline 2. Make the original story more focused about gore and violence maybe? (The magical girl in the TV uses guns lol). Before those lines of thoughts, the title seems very familiar to one I read a few weeks ago. In which everyone got into Alice box and both side's roles are reversed. Can't find the link between this and that so far tho