Okay, so I'm going to take the road I usually take with otome games. I will sum up my feelings about each character in a gif. If I feel the need to say more/add another gif, I'll do so.
C-TEAM
Carlos:
No lie, I thought he was gonna be this kind of character on first glance:
By the end of the game, he turned out to be a guy who just wanted to do good and save everyone, and he just kept fucking up. He got put through the wringer, and I'm glad he got to give Zero his last rites.
Junpei:
Yes, he was broody as fuck in the start, but I figured shit went down to get him to that point. He didn't become Tenmyouji overnight, after all. I did go 'what the hell, Jumpy?' a couple of times, namely at the first vote to eliminate a team, but overall, I was gad to see old Junpei come through as paths progressed.
Akane:
She was the most stable girl in the game (when Junpei wasn't being killed). When it came down to brass tacks, she did what was needed to get shit done. This includes the end when she made Junpei forget about her. Ice cold. Plus, in the end, she and Junpei finally got their happy ending, so that made me happy. If anyone deserves it, it's those two.
Q-Team
Sean:
He never asked for any of the shit he went through. I wanted to hug him so many times.
Eric:
Mira:
The Q-Team as a whole was interesting to me, but Mira stuck out. At the start, I figured. "Oh hey, it's the sarcastic chick with the big tits, how original." Cue me sitting there, hand over my mouth, eyes big as saucers when her reveal dropped.
D-Team
Diana:
I get the feeling Zero/Delta made her the leader of this squad specifically to die at her hand later on, especially in the ending where he killed Eric, Sean, and Sigma in the computer room. Either way, poor Diana was another character put through the wringer, but came out at least a little stronger in the end. I just wished the game had given the whole team a proper epilogue, dammit.
Sigma:
Sigma is an old man that needs rest. He's been through a lot, moreso than most of the other characters. At the end, he was probably just like this:
I hope he took time off to spend with Diana and Phi.
Phi:
Nuff said. My favorite character in the whole damn series by a clear mile.
Lest we forget...
Zero/Delta/Brother:
Was he a dick? Yes. But there's also a complexity to him, as he himself stated, that made him an intriguing, memorable villain.
This is my GOTY for 2016. Nothing can best this.