If we exclude that special episode then this was an awesome series. That special episode felt more like a teaser for Season 2 rather than a conclusion to the series. The series itself is a bit difficult to understand at first but once you get into it you'll definitely enjoy it a lot.
Although remember that there isn't any proper conclusion to the story.

After the first episode the writing nosedives into mediocrity. The characters are so boring, they made episode 8 a recap of the four characters and their personality types, so you would actually think they had personalities. In the end everything the girls did in the story was pointless. It was all a big subplot misdirection from the writers to lead the audience to an even worse written story.

This was a great anime with a very unique concept, but like many others' opinions, the ending kind of ruined this. If they stuck the landing with the ending, this could have been a solid 8/10 or 9/10 show, but with such a lackluster ending I can't give this anything higher than a 7/10. People should definitely watch this series, but whether you watch the final special episode doesn't really matter actually.

Great animation, good premise and well fleshed-out characters. the first episode really hooks the viewers in and from there on its a rollercoaster ride. This anime does a good job exploring different personalities realistically and not falling into the pitfalls of any stereotyping. It also delves into taboo topics in a very matter-of-fact way and doesn't dramatize the topics itself, just the emotions of the 14-year-old main characters (which, if we're being honest, is a very dramatic age for them anyway so it fits real well). If I were to criticize anything, it would be that the overarching plot wasn't very conclusive and left me with a lot of questions (some of it answered in the special). I was left wonder wait, that's it at the end.

Regardless, it's a really captivating watch and I recommend it to people who are in to fantastical psychological thrillers. If you're happy believing children are meant to be and should be pure and innocent, this is not for you.

100% Worth the watch. I recommend skipping episode 8 and stop after episode 9. 8 is just a recap, and the turn from episodes 10, 11, 12, and the special will only disappoint you as it undermines the heart the show stands on.