A boy who can get sentenced to death for coughing, barfs loudly in public.
Series in more sentences:
The struggles of Rin continue after he's been revealed to be Satan's son and put on trail for it. The council believes he might be the only one who can defeat Satan himself and they allow him to live, for the time being. He's put on a leash and ordered to keep his true nature hidden from the rest of the world, giving him little to do while his distant friends are involved in the action.
Rin can't control his newfound powers very well, but realizes it's his time to shine when a legendary threat emerges that will possibly kill the entire area in one blow.
As for this part, I flew right through it, but I don't think I liked it more than the first. Rin had very little screen time and I found his relationship with his brother to be emotionally distant. His brother is a lame, overcompensating, jealous caricature of an adult who won't even give the person he knows is a good guy a smile. But I'll be honest to say that I can't recall what they were like in Blue Exorcist. It's been 5 years I last saw it and I didn't feel like revisiting it.
This season did its best to remind you of what happened previously and who is who, but of course some things stayed vague to me and the new characters got little development. So did some of the old ones; Rin's love interest was really pushed to the back, while I would've liked to see these two interact more. I believe the original series also gave us little, as this girl simply doesn't love him like that.
I don't remember the villain, either, so I'm assuming it's one of the new guys. I liked his abilities, but not his motives. They don't make sense to me. I also wondered what we needed the doomsday plot with this other monster for, who ended up very easy to defeat by our Satan boy. It would've been better if the main villain got fleshed out and the crew had to fight him.
I imagine this isn't all we'll get to see of Blue Exorcist, though. I hope the next episodes are going to be about Rin, and not all those other faces.
Also, seeing him get friendzoned is the saddest shit any TV-show has presented me.