See, I just don't think that Tengan would have killed. It doesn't seem to me like he would have approved of it. If he killed Chisa, he would know that this would further spur Munakata towards extremes - an act that he has no desire to have happen. Further, it would be anti-climactic if the person that killed Chisa could not be confronted by Munakata when Munakata learned the truth. I do agree that Tengan was the one who woke up, but for me, it makes more sense to believe that Tengan woke up on the second night phase, chose not to kill, and instead Monaca/Miaya killed the Great Gozu. This is the most plausible explanation for me, especially when you consider that the rules make the explicit hint that someone besides the traitor is awake during the night phase.
So far, the second killer is the only one I'm sure of, and the second traitor is the only one I'm sure of. Munakata being the traitor/killer on the third night phase does seem plausible, but I'm leaning towards the idea that Seiko killed herself - which would make sense given the tone of the scene.
The first traitor (and presumed killer) I am not sure at all about.
1. Juzo could be it, but he's a bit too much of a knucklehead. His association with both Chisa and Munakata does leave open the possibility.
2. Ryota is very suspicious and dodgy
3. Munakata could be playing the long con
4. Chisa killed herself
5. Sixteenth participant
6. Koichi; though while I consider him suspicious, I do not know that I suspect him of killing anyone, just of being the mastermind.
As for them being hanged from the ceiling? Well, the answer is simple:
The killer isn't the hanger. We do not know the cause of death for any of these characters yet (Tengan and Bandai aside - speaking of which, I very much suspect something relating to Bandai, just because he, like Mukuro, was made an example of - though not in the same way). My theory is that the sixteenth participant cannot be affected by the sleep drugs, and is in fact responsible for hanging the participants who have been killed during the night phase. This is, of course, assuming that the killer alternates; another possible answer is that the killer's NG is "killing someone without hanging their corpse".
I really do think the NG bracelets force the participants into killing. They go asleep, the killer is woken by the bracelet, and given a kill or die ultimatum. there's no single killer. Chisa, Gozu, and Seiko were killed by different members of FF.
It's the best way of showing the world how easily the world's hope, the future foundation, are corrupted. I also agree with Gozu potentially being chosen as the killer in ep2, only to refuse, letting monaca and the true mastermind kill him via his bracelet, string him up and play a prank on Makoto in the process with the one they intended to die - asahina. I think Kyoko will work this one out - we can't see the effects of the poison behind the mask.
I just do not see it. The thing with it is, the only way that Tengan could know what he knows is if he was one of the people who woke up, and only two of those people exist. Therefore, he either woke up on the first phase and killed Chisa or woke up on the second phase and killed Gozu. As I discuss above, I just do not see Tengan killing Chisa in particular, because it would not benefit him (and he would have known this). The situation would only grow more dire with Munakata and drive him further into despair. As for the second night, I do not see Tengan ritualistically hunting down and killing the Great Gozu, particularly because he, to his death, was very much on Makoto's side in all of this, and killing Gozu would also not benefit his goals. Therefore, Tengan must have been awake during a night phase, but the people who died during this phase are people he would not have killed.