Watched ep4.
Total spoiler here:
X wasn't too hard to figure out just from the looks, and on-screen time (LOL, I used that method when watching Kindaichi!). And I figured X's plan after hearing Akiyama's basic plan.
But I didn't expect Akiyama's final plan. Though I did think it was weird, since the basic plan had a lot of leaks. Like what if one of the members turned on them, or one of them used Akiyama's plan with another group of people instead.
Total guesses here for part 5. Akiyama's folding note was to lure and confirm X. And I think it will eventually become a group-up of the three against Akiyama (because all three seem greedy, and fear Akiyama can make a plan to win it all). Although I think the grouping will also be their downfall. I also think Akiyama will be able to pull of a suprise by grouping with one of the 3 beforehand without the othe 2 even knowing (kinda using X's plan).