It's really good. I'm pleased to have watched it and I'm looking forward to Season 3.
It's an anime about virtual reality MMORPG (Massively Multiplayer Online Role-Playing Game) worlds. Season 1 had all the main characters stuck in an MMORPG that killed you in real life if you died in the game. Season 2 has solved that problem... or so everyone thinks. Our main characters are Kirito, Asuna and their adopted AI daughter Yui, plus friends like Sugu (Kirito's sister), Klein (friendly, a bit of a goofball) and a few others. There are about half a dozen of them, often adventuring together and occasionally a bit hard to tell apart. You can change your virtual avatar's hair colour and even facial features, while on top of that the girls have similar anime-style faces.
Season 1 adapted two story arcs: Aincrad and Fairy Dance. Season 2 has three: Phantom Bullet (novels 5-6), Calibur (a side story from novel 8) and Mother's Rosario (novel 7). They're all very different. Phantom Bullet is strong, traditional Sword Art Online. Calibur is a bit pointless, but it's only three episodes, so who cares? Mother's Rosario though is something genuinely different and beautiful.
The show's problem is that, in-universe, people have smartened up. The NerveGear technology in Season 1 had a bug, i.e. it fried your brain and killed you. This fails health and safety standards. It's since been replaced by AmuSphere, which people are much happier to use because it's safe. This makes sense, but it also reduces the danger level, because virtual death now just sends you back to your last save point. These stories' challenge is how to make the show exciting and dramatic despite this.
1. PHANTOM BULLET
This arc lasts slightly more than half the season, even without the highly skippable recap episode (14.5). In short, someone's worked out how to kill again. A skull-masked player called Death Gun is shooting people in virtual reality, then in real life they immediately die of heart attacks. This is impossible. Everyone agrees it's impossible. However Kirito goes to investigate anyway.
Unlike the first two worlds we visited, which were fantasy, this is a deliberately unpleasant game world. It's called GGO (Gun Gale Online) and it's a gun game set in a vaguely post-apocalypse urban future. The whole point is shooting and killing other players. Playing a psychopath isn't just normal, but encouraged.
Season 1 was about love, but this arc is about killers. Both Kirito and the new character, Sinon, have ended lives (in the real world, not just in-game) and are still living with the guilt. Sinon has panic attacks if she's even reminded of guns in real life, despite being one of the deadliest snipers in the game. There's the guilt of remembering what you've done, but also the guilt of forgetting. The exploration of this and the catharsis at the end are emotionally strong.
Then, obviously, there's Death Gun, who not only remembers all his murders but wants to go on committing more.
This is really good. It's nice to have a character who's not in love with Kirito in the slightest, but instead has other problems to deal with. Sinon is broken. She needs professional help and she's trying to heal herself with bullets. It also fits thematically with the setting, with GGO being a world of killers. Swords can be used for defence, but there's no use for a gun except to put a bullet in someone.
It has some clever and really creepy ideas. Death Gun's killing method will make your skin crawl off your body and roll into a ball. It's also quite exciting, partly because of the difference between games and reality. The action scenes are surprising. Game tactics differ from what you'd do in real life, with dodging bullets and even swiping them aside with a sword being permitted game actions. (Kirito, being Kirito, chooses as his main weapon a lightsabre. It even makes Star Wars noises. Even in a gun game, Kirito wants a sword.)
It also has a little humour with Kirito's GGO avatar, which here looks female. Yoshitsugu Matsuoka (Kirito's voice actor) never camps it up, but he does have a little fun when Kirito decides to play up to his image. That was welcome light relief in what's otherwise a dark story in a grim setting.
I was overly harsh on this in my Part-One-a-thon a while ago, by the way. Ep.1 is mostly set in the real world (which is anti-exciting) with a few scenes set in Gun Gale Online (which is actively off-putting), while its characters are spending most of their time analysing virtual reality technology and questioning whether or not people are getting killed when they die. Fortunately it improved.
Our heroes go on a game quest. That's it. For three episodes.
I laughed at the three Norse goddesses being Urd, Skuld and Belldandy, though. Yes, they're the three main Norns, but I'm afraid my first point of reference is Oh My Goddess.
3. MOTHER'S ROSARIO
It's an Asuna story! Yay! I like Kirito, but it's nice to have a break from him and focus on one of the girls instead, especially since Asuna had been sidelined in both the second and third story arcs.
Gaming's still non-lethal, mind you. It doesn't really matter. It's a game. It's all for fun. This even gives us a nice character moment for Asuna, when she realises that her attitude to game combat is still affected by the days when fatalities were real. However this doesn't matter at all, because this story arc is reminding us that stories don't have to be about danger and life-or-death battles. Asuna makes some friends. They want to do something that's completely unimportant in the grand scheme of things (beating an end-of-level boss), but it matters to them and that's what matters. When other players oppose them, that's inherently more compelling than trying to overcome a computer-generated opponent as in the Calibur story arc.
What's more, Asuna's friends have good reasons. Very, very good reasons. When we learn what those are... gosh. That was clever and emotional.
We meet Asuna's cold-blooded, controlling mother, who really will make you feel sorry for the poor little rich girl. We also meet a stronger fighter than Kirito! Yay! I like Kirito, but it's unhealthy for heroes not to get beaten occasionally. The game stuff is good, but for once it's the real-world material that's important, which is a welcome novelty in Sword Art Online. The anime's shuffled the order a little since Calibur came after Mother's Rosario in the novels, but Calibur would have been a weak ending to the season, while this is heartbreaking and beautiful. It improves the series just by existing. Had the show continued along the lines of the first three arcs, it would still have been good, but it would have all basically been the same. Mother's Rosario is doing something different.
I really like it. I really liked Season 1 too, but Season 2 is just as good while broadening the show's dramatic range. The new characters are memorable (Sinon, Yuuki) and the show remains both exciting and thematically strong. You can probably afford to skip the four episodes from 14.5 to 17, though.