I think they're adorable! If any of them, I'd probably get NL, RAINBOW or A BEST.
I really love the idea of them, the only downside is that compared to a regular mp3 player they're kinda useless............but they're still awesome gift ideas. A backpack covered in these would be awesome!! <3 If they'd only come out when I was still in school...........
Are they only limited things or will they stay in print? The wording's a bit confusing....maybe when I finally get to Japan I can buy one