It does seem like this is Mijumaru's capture episode, rather than Meguroko's, but what's odd is that all the footage we've seen of Mijumaru has been in grassy areas (I think), yet the only clip we have of Meguroko is in a very rocky area. While this doesn't necessarily mean anything, it might be that Mijumaru is caught before, and the group (whoever that may be at the time) move on and reach this more rocky area with the Meguroko. I'd love it to be a Meguroko capture, but I don't see it as particularly likely.
And although it might be a bit early, perhaps 'Critical Moment' might be the activation of Mijumaru's Torrent or something (though I hope not, frankly I've had enough of blaze, and I can't see torrent being much different!)
By the way, how do we know this is the third episode?