Finally caught up with all chapters, yay binging 69 chapters in 2 days. And these are nice long chapters too... none of this 10-15 page shit. Anyways!
Yeah, obvious twist that the Idol is "secretly" a betrayer is obvious. I don't believe for a minute that the "only people who can make it this far are either completely honest or completely dishonest". Everybody else has to be completely dishonest, and the people from the MC's group are only around because he's so batshit crazy and conniving that their honesty (the big tit girl, anyways) is being compensated for. Also, for a genius, that guy sure keeps getting fucked over by other people by figuring shit out that he didn't see coming from a mile away. Maybe a genius when compared to normal people, but he's far too overconfident all the time.
Also, something tells me that big tit-chan is the real secret betrayer behind everything. She's the only one we haven't gotten a huge backstory on, other than she had to prostitute herself out when she was younger which... when compared to killing people or having your parents killed, is really nothing. So she's still hiding something. There's no way the MC is the real betrayer (unless the mangeka is pulling the wool over *all* of our eyes... which is possible, but I kinda doubt it.) The lawyer glasses guy already said his motivation early on, and that's enough of a backstory to me (I doubt there's more to it than what we've seen... but it's possible, this manga loves turning shit on its head.) The rich kid is just some virgin rich kid who has the hots for big tit-chan, so I definitely don't think he's the secret betrayer. It's... possible... but I don't think he's the one.
So in order: Big Tit-chan, Lawyer Glasses-kun, Virgin boy, and MC.
I think Soldier guy is the one who shot Genius boy, but I also don't think it'll be enough to take Genius boy out, since it's only for a minute and it's likely the zombies aren't nearby... so I think it'll be a wasted bullet in the end.
