Near as I can tell, FEN Guide existed for the native civilian population of Tokyo, Japan, who wanted to better their English speaking, reading, and writing skills, especially when used alongside what was being broadcast by the Armed Forces Radio and Television Service (AFRTS) on the Far East Network (on the AM dial: 810 KHz in Tokyo). More information about the station can also be found on the AFRTS Archive here.
My Dad was stationed there as a Navy Journalist from June of 1984 through May of 1987, hosting shows like East of Midnight, Day Trekker, Kanto Scene, and co-hosted Pactrax 86 with Gerry Galipault. He also sat and produced for news and PSA spots for the television station (most of these were dubbed to Betamax, and I'm working on conversions).
At some point, I expect to have dubs of a few of his shows which survive uploadded to this site (rendered inoffensive to copyright strikes, of course).
FEN had a fairly large listening audience, and dedicated radios were even sold to accomdate this audience (the magazine features advertising for small ones, tuned only to FEN, for about $23 USD at the time, made by Sony).
I'm not certain how long the magazine lasted, but I would be very interested in more information about this or anything else to do with FEN from the time my father was stationed in Yokota. There are a number of ways to contact me, but email is probably best.