Story: 9/10
One thing I really enjoyed about this season was its lack of clear-cut arcs which so many anime seem to have. There's nothing innately wrong with having arcs; the issue is that it often prevents genuine character development. The completion of an arc usually means the main character of that section is now irrelevant, and the nature of having arcs means that character, or characters, will only have just that one arc to develop. By avoiding this convention, Oregairu allows our characters to develop over all 13 episodes, not just 3 or 4.
Plot wise, the story picks off immediately after the first season. Hachiman and the girls go back to doing their Service Club duties, except this time Hachiman's methods will not go unpunished. His tendency for self-sacrifice may sit well with him, but he'll soon learn that self-sacrifice doesn't only hurt him, but others around him as well.
This may give the impression that the second season is depressing. It's not, but it is definitely more serious because we'll see the bonds of our three beloved characters really put to the test. Think of it as a more mature version of season one.
Art: 10/10
The art is actually really good. You'll see a major difference between the two seasons.
Sound: 10/10
Solid opening and ending themes. No complaints.
Characters: 10/10
Honestly, this category deserves an 11/10. You'll witness a great amount of growth in Hachiman, something that I actually saw some people disliked. Many people have claimed he's lost his sarcastic and pessimistic attitude, something that attracted all of us to the show in the first place. To be honest, this is sort of true. He's less sarcastic, but only because of how much he's matured. He's come to realize that "youth is a waste" isn't really accurate, and that trying to maintain this apathetic attitude doesn't bring happiness to himself nor the people he cares about. Watching him grow from his trials was extraordinarily satisfactory.
His journey means he has drastic effects on the people around him, however, and you'll see how Yukino, Yui, and the others are affected by it, for better or for worse. Can't really say much more without spoiling it, as the show is heavily character-focused.
Enjoyment: 9/10
Just really perfect development of characters. Sometimes I wish the show was more light-hearted like the first season, but it's by no means a serious drama or anything. It's still the characters we know and love, but now they've grown up a bit, and it's been fantastic to watch.
Overall: 10/10
If you're a big fan of season one, which I know a lot of people are, you will fall in love with season two. Definitely a must watch from Spring 2015.
If this review was helpful, please say so! If not, I'd be glad to know how I can improve.
