[godwine]

Display case filled with japanese toys, Chogokin etc

Get a larger display case and put a small scale model of a district with running trains.......... a friend of mine was doing something similar with his sushi store, its not in a display case, but model building along the wall and tracks along the wall, so the train travel around the entire complex..

Use one of the Train station chime as your door opening/closing melody...

Decorate the entrance of the place with something that signifies japan: Tori, Yamanote train entrance (you will need the full aluminum and gree theme to pull this off) etc

Thats about all that I can think of.... one of the forum members can probably tell you where you can order a bunch of japanese toys and stuff.. I use Rakuten myself for the most part, and I use Tenso to have stuff redirected...