It took me ages to get around to watching this. I didn't really want to. Season 1 is very good, but also not a particularly comfortable watch. It's the story of Rei Kiriyama, a schoolboy who's also a professional shougi player. ("Shougi" is Japanese chess.) There's a lot to love in the show, but Rei himself had a ton of personal problems and the kind of personality that's making them ten times worse. He could barely talk to people, he couldn't make friends and the most self-effacing nothing you ever met. Even his name ("Rei") means "zero". He couldn't even imagine being happy.
That was at the start of the series, though. Rei's got better since, to the point where I actually enjoyed watching it and I'd be quite enthusiastic if they made a third season.
Firstly, he's acquired friends. His fellow professionals like him and he has a small, loud, round wannabe-rival in Harunobu Nikaidou. The two couldn't be more different, but Nikaidou thinks Rei's the greatest and is endlessly supportive. (The character seems to have been based in part on a real shougi player, Satoshi Murayama, who had health issues and died at the age of 29.)
Secondly, he's effectively acquired a family. It's his third family, incidentally. His biological relatives are dead, while his "siblings" in his foster family have gone bad and are bitter with resentment of him. Now, though, he's become attached to the Kawamoto family. (He did his best to stay away, but they could see what a hopeless case he was and absolutely refused to leave him alone. By this point he's accepted it.) There are three Kawamoto sisters (Akari, Hina and Momo) and a very loud grandad. Akari's effectively the mother, in the absence of any real parents. Hina's in middle school and Momo's not yet started school at all. They're all lovely, but they're also quite short of money and they Take Things Very Seriously. They'll react to food with the intensity of Romeo having a rendezvous with Juliet, while their opinions of Hina's new haircut in ep.44 made me laugh aloud.
"When did I come out into this warm place?"
The show's about social isolation, I think. Rei's obviously the poster child for this, although he's improved a lot. Hina, of all unlikely people, will get bullied at school, in a surprisingly hard-hitting story arc that's telling it exactly as it is, not as anime would often like it to be. The victim will get blamed, even potentially by the authorities. (That teacher, bloody hell. She's arguably worse than that bully's evil mother.) People will be destroyed, if not literally (i.e. suicide) then by trauma for someone who often didn't have much self-confidence to begin with. Hina gets it bad, but another girl gets it worse. The aftermath is comparable with PTSD. The problem isn't just the perpetrators, but all the people who know what's happening and think that trying to help will make them the next target. There's detailed, realistic discussion of your options in this kind of situation, including reasons why some of them might look good but make things worse.
That was a strong arc. It'll make you angry, but then by the end you'll have wanted to cheer.
There are other embodiments of the theme, though. There's Souya, the genius who's beyond the reach of any other living player, but wouldn't necessarily pass a Turing Test. There's a scene in ep.36 where he barely seems sentient. (There's a reason for that.) Similarly, Nikaidou was a perpetual outsider as a child due to his rich background and health issues. Loners and weirdos are pretty common in the shougi world, in fact.
It's an intelligent, sometimes powerful show... but this season's also funny. It made me laugh, especially in the last few episodes with the nagashi soumen, Hina's haircut and Akane's employer's concern about Rei. I loved grandad in ep.43. I worshipped the headmaster in ep.34. (He's a god.) I'm looking forward to the 2017 live-action movies, even though they're both nearly two and a half hours. If you were on the fence about this season because you'd struggled a bit with Season 1, jump off the fence and give it a go.