I really liked this ghost arc and this concept, it brought some mystery to the story and it makes the reader curious about who the killer is and how he goes around killing for so many years without getting caught and if he's a stand user or not
Now we all probably know who he is, but still I find this idea good and I really saw how good it is while reading the manga
To be honest part 4 didn't really make me really like it at first but now I'm kinda really getting into it, maybe I watched the anime too fast or something like that, but I feel that I'm starting to appreciate part 4 more