Man, what an amazing manga. I don't even remember the last time I was engaged and immersed in a story like this. I just loved the intricate plot, and everything else. I found myself reading 6 volumes at one setting. I surprisingly found myself tearing up or getting emotional in certain scenes, which was a good sign for how believable some characters were. It's differently better than Monster. Monster doesn't hold a candle to it, in depth, level of details, plot twists and execution. Actually in literally everything (I don't think I ever even liked a character in Monster) and I certainly think Friend is a better antagonist than Johan. It was just more focused and handled the sub plots way better. I think the author is a great writer, he just have bad habits that I have noticed in both of his works. But that's just my opinion.
Now the things I didn't like, was without a doubt the third part of the manga/the second time skip. Like many others in this thread, I really didn't like it. I thought it wasn't necessary how it dragged out stuff, and brought many new plot points and events, I personally couldn't care less about the sci fi aspect of the series and it just dimnised my interest because I was looking for a conclusion but things kept dragging, with new characters, that I simply can't like or be bothered with. I found myself skimming through certain chapters due to me being annoyed. I didn't like the handling of Kenji's character at all, he barely feels like the old Kenji, which might have been the point but I still didn't like it, and all that song crap. And Kana definitely have gotten worse in the second time skip imo. I mean I already didn't like her teenage self, but the second time skip, made me just flat out dislike her and find her annoying, I'm not saying she is a bad character, but I just couldn't sympathize with her. Kid Kana is best Kana, she was so adorable <3.
Anyway, I can't bring myself to give this lower than 9. I feel like I can say it became one of my favorite manga, despite the latest portion of the story. The first 100+ chapters were just too good.
9/10