Neo Tokyo haven't been ported because the storyline is too intertwined with Japanese culture/cities. If ppl on this forum recognize the following
-Tsukuba City
-"We can't shut down Rainbow Bridge!"
-Gundam/Neo Genesis Evangelion ("Neo Tokyo")
You wouldn't get the references. Plus it has "Breaking the DMZ" which is like shouting the n-word to Blacks
Kaede Castle is standalone. I'm guessing the dev team over at Nexon Japan developed KC and based on its success, built a bigger area and weaved KC into it. KC has nothing to do with the Neo Tokyo storyline and its only connection is to serve as a prequest to starting Neo Tokyo quests (req. some KC drops)