I'm super happy that the second season was successful instead of it being a total dud compared to other second seasons I've watched. Right away I can say the animation definitely matured since the first season. The colors are a little more dull, giving the show a more ominous atmosphere, which played perfectly with the plot.
The plot was amazing. I loved how we got some more of Art, Nice, and Hajime's backstory. Even though I hated it, Art was a great villain. His motives were legit and understandable, unlike villains I have watched in the past. I really don't want to spoil the ending, so I'm just going to say that it was FAR better than the first season's ending. THIS was the ending I was waiting for and I am so happy that the show ended the way that it did.
As for the music, I specifically liked the theme song. It always got me riled up for the episode because it was so upbeat and catchy. I always found myself dancing in my chair or slightly bobbing my head to the beat. That's when you know a theme song is good.
Overall, this short series has really touched me and I'm very happy to have watched it and come to love the characters.