Kit,
I think that you're exactly right in asking that question. I've not seen anybody (I live on and off in the US and Japan) who dresses this way.
The only thing that I can think of is that Kikuchi was attempting to mix some of the current, popular European designers, elements of Etro, Galliano or Viktor & Rolf or Hedi (that tie over the polo shirt and the super-skinny trousers) with the Japanese aesthetic of quirky layering, combinations of colors/patterns that "clash", etc. Also, conveniently, these designers are REALLY popular in Japan right now.
Unfortunately, I just don't think it worked well for him. I don't see anything in this collection that works as a whole. Individual elements are sometimes interesting, but I think they don't work together. It seems that he tried the old formula "Galliano works. Etro works. So does Comme des Garcons. Therefore mixing them all together must work." But... of course... it doesn't.
To be honest, I don't view Kikuchi as much of an original designer in the first place. In Japan at least, he has LOTS of stores that put out mass-produced, low priced clothes that copy the latest trends. While I'm sure that this collection is higher quality and higher priced than his mass-produced stuff... nevertheless it still seems to me to be simple "sampling" of trends without a real, underlying idea.
John