I'm pretty sure the second from the left is supposed to be Canada, not Britain. She's holding what looks like the Kumajirou teddy bear that Canada owns and she has Canada's purple eyes. See Kumajirou_(hetalia) and post #535021 for reference.

I won't edit it myself since I can't read Japanese and I don't know if the tags/description on Pixiv say otherwise, but maybe someone else can clarify.

Yeah, That's defiantly Canada. I'll change the tags.
Also, odd choices for the character switch in my opinion.

Romano/Kyouko - The brash one.
Canada/Mami - The polite one.
Veneziano/Madoka - The ditzy one.
America/Sayaka - The "wants to be a hero" one.
Japan/Homura - The stoic one.

Kinda works. :|