It's a romance between 1990s teenage gamers with the social skills of woodlice. (But they're adorable woodlice.)
1. Oono never speaks. Literally. I'm in awe of how well the anime brings alive this self-imposed mute. People have "conversations" with her and these scenes work. She can even be funny.
2. Haruo is a boy who loves games, games, games, games, games, games, games, games, games, games and possibly Oono, but it's taken him 15 episodes to kick his brain alive even to that small degree. We'll discover that he's not completely unaware of horniness and the facts of life, but mostly in the sense that rodents are aware of aeroplanes. What's that thing shooting over my head? Well, never mind.
3. Hidaka is a girl who fell in love with Haruo. What more can I say?
Obviously, you need to watch Season 1 and the eps.13-15 OVAs. You'd still understand the story if you didn't, but why wouldn't you? It's all good.
There's romance, but also a loving examination of 1990s gaming culture. (No names were changed, by the way. It's full of real games, their characters and even their authentic 1990s computer renditions. The manga was temporarily slapped with a lawsuit from SNK Playmore in 2014.) This includes dorky bits of that culture, e.g. Haruo going through the teenager equivalent of a mid-life crisis in ep.17 and hanging out in Shibuya while dressed as a delinquent. Also, Haruo and Oono have guardian angels who talk to them and give advice in times of trouble. These are Guile and Zangief, from Street Fighter II.
The love triangle is played for real, but it can't be separated from computer game duels. These relationships are defined by gaming... no, more than that. They're built from them. Haruo overdoes his decision to tie a big confession to a SF2 tournament battle, because he's Haruo.
The animation's still cheap-arse CGI, but in a good way. The show's unashamed of it. The visuals aren't trying to represent reality, but instead are happy to be their own cartoonish, simplified selves. The important thing is that the characters work and you can engage with the emotional acting.
It's great. I love all three characters. I love the weird things outside the train in ep.22. I love Hidaka talking absolute filth to Haruo and making it impossible for him to dodge what she's saying. I love Oono's loud sister. I love the ending, although obviously not everyone gets what they want and our the heroes still have major problems ahead of them. This is a lovely little show.