[crazysjd89]

It might be hard for Kasumi to keep up the act, but I think she had enough hatred to do it. Plus, when she's not being bad-mouthed, or angered, she is really calm. Kyrie only very rarely speaks during the Family Conference, anyway.

It's a bit farfetched, perhaps, but I think Kasumi's determination could do it.

This part isn't logical evidence of any sort, it's just something interesting to think about:

Spoiler for Episode 4:

Kasumi was being possessed by Eva-Beatrice. As I said, not real evidence though, since that was saying that she got taken over by black magic and the dark witch.

However, I feel that most other explanations are also a low probability, mostly George's death.

I can understand why someone who wasn't truly dead would kill Nanjo, since he claimed they were dead, but they weren't.

But I cannot think of a good reason to not only kill George, but also inscribe that number on the door also. Considering that they must have lost a lot of blood and was on the verge of death (assumption), I don't see how they could have gotten the energy to do it.

Then of course, you could say Eva killed George. This is possible, but I find it really hard to believe Eva would kill George, with how much she dotes on him.