Amethyst

I'm not a fan of this episode. It seems to flawed/lazy.

"Kaito: you could reach the tube with a pole but not with a rope. " a bit later ryoma gets wacked with a stick. If it is too short, pick some rope and tie two off them together. 

The rope was found by the tank. How did that happen? Kirumi would have to jump down with the rope because you need to untie the middle. After that you can't get the rope back into the gym at that spot. Convenient they didn't show that part.

The culprit made almost no mistakes only two so it must be Kirumi. Left the handcuffs (for no reason), didn't put back the wire, left the tube, left the fabric (which she would have noticed). I'm especially miffed about the last two since she didn't even try to get them back even though she had at least half a night to get them back. She made a whole complicated murder plot in less.

etc.

It's basically the problem with forcing to fail OP characters (Kirumi was OP), it makes absolutely no sense for them to fail. So even though the logic is flawed this episode was enjoyable just for your reactions.