This sounds like a very good idea!
If you were to bring it into Japan would you be using many of the superstitions and legends that surround it??
I understand what you mean, character development and design are often hard to make. I usually have a problem with creating names for the characters, I will have everything else made but i can just not think of a good name.
Good luck with the story!
I hope you post it on here, either while you work or when its done, I would love to read it!
(If you need any help at all I can give you a hand.