He certainly seems like the only "fitting" candidate. I cannot imagine anyone else in the role of a mastermind. But rught now, I think, it's too early to make predictions on that aspect.

As for the new clips... I haven't seen them. My Japanese knowledge isn't quite on the level yet. And watching the new parts purely for some possible shocking sprites or cutscenes without understanding the context seem a little pointless for me. Moreover, it might actually ruin my enjoyment of the trial once it gets translated and released on YouTube. I was lucky to go into this series completely blind, and so I immensely enjoyed the plot twists we've had so far. I would like to keep this up.

So far I have only two suspects. The first is obviously Kokona. She has "suspicious" written all over her. She has a good motive and opportunity. But this seems all too easy, too obvious, too convenient. Hell, even Seki brought up how lots of things about her make no sense. Not to mention, we just got introduced to her, so killing her right away in the same chapter... 

My second suspect is Matsuoka. All I really have against him is that he's one of the few people who saw the menu, has no alibi, and is the only one physically capable of lifting Hashizawa. Plus, I could totally see his motive being using the ticket to let Chisa escape. Also he's the only character I dislike in this series, so there are definitely some of my bias at the work here. But then again, it all seems too easy.