They exist outside of the Japan too.
It's called Lolita Fashion - http://en.wikipedia.org/wiki/Lolita_fashion
They have lots of different sub styles - Gothic Lolitas, Sweet Lolitas.
Generally from what I understand they're their own sub culture outside of Japan, but they're not uncommon at anime / manga events.
The retailers at these events already sell Japanese sweets, even the seasonal and limited edition ones. In the US JBox.com – and their NSFW parent company JList.com are probably the biggest retailer of such candies in anime / manga fandom.
JList buy candy in bulk from wholesalers and advertise heavily to anime and manga fans. They have a generous affiliate banner ad scheme too, which means lots of sites link to them. As Candy Japan expands I imagine JList would be a primary competitor for selling Japanese Candy. They already have the market share and infrastructure in place, with offices in Japan and the US. I'm sure there is plenty of room for competition, but I'd be aware of them as a business rival in this market.
JList buy candy in bulk from wholesalers and advertise heavily to anime and manga fans. They have a generous affiliate banner ad scheme too, which means lots of sites link to them. As Candy Japan expands I imagine JList would be a primary competitor for selling Japanese Candy. They already have the market share and infrastructure in place, with offices in Japan and the US. I'm sure there is plenty of room for competition, but I'd be aware of them as a business rival in this market.