Currently Airing Anime

 Spoiler

It'll probably last for 2-4 more episodes. I imagine the only way he'll break out of it is because of Inori, but not because she dies. She's the main heroine of the series. Though I can definitely see them killing off a few more people before it ends.

As far as the OST goes, my favorites are Hill of Sorrow and Ready To Go. Though I like most of the OST.

 Spoiler

I meant losing friends as in connections so he becomes isolated. I just don't want it to last forever then he comes back to normal for the last 1-2 episodes.

I don't see them killing off anyone else, but probably extremely wounded which would snap him back (inori). Also, i think they need to have more plot with his mom because so far she hasn't done too much for the story but they didn't put her as a GHQ member for no reason.

I hope there's gonna be an OST #2 because some of the songs, especially the one during episode 15 that I was looking for earlier, isn't on the OST that was released.