Its been a long time since I read from this author, probably the last one is uwakoi. I feel like I have seen this in hentai, I think its title is "Cage", the plot is exhibitionism that is spreading in school.
This ending felt like a completely different writer hijacked the series. It was totally unexpected...but was it bad? I’m still too shocked by the direction change to feel anything else but the confusion caused by the final chapters.