Some of these suggestions are great!
I have a gay Japanese friend who has told me some things to look out for when trying to find a gay Japanese man, but since he is only interested in a certain type of guy I only got the info on a type called gachi-muchi which are thick or muscle bound guys, I don't know if this is specifically a gay term.
but gay gachi-muchi boys fashion tend to mimic american style, button down shirts,tight t-shirts, rugby polo. Vodix is a gay Japanese brand that caters to this type of guy: http://www.vodix-jp.com/
so some Japanese guys follow a specific look to show their gayness while others might be just dressing like their favorite actor which they call ikemen, this is a general label for a good looking man but if you google it you find alot of prettier guys, styled hair, very fashionable guys etc. so yeah it's hard to really know unless you ask or find out somehow.
Also, Japan is awesome especially if you have an interest in it. I've only been a couple times but both times were a great adventure, I never had a dull moment.