I think the reason Japanese people love Crocs (which I find abhorrent) is because they're just the right amount of shoe. In New Zealand, what others call flip flops, or as Aussies call thongs, we call Jandals, and from what I heard, it comes from a Japanese sports team wearing what was most likely geta, and then the Kiwis put 'Japanese' and 'sandals' together. These days you don't see geta that much, and the same with jandals as well, unless you're at the beach.

Crocs on the other hand, are pretty popular. Crocs have a huge advantage in that they're easy to put on, people in Japan generally loosen their shoe laces if they have them to make them easier to put on and take off (meaning they don't always wear shoes properly), and they are almost the perfect mid point between jandals and shoes meaning they're great for summer. I think they're also just enough shoe, so that your feet don't also get as dirty as Jandals or sandals for that matter.