There's one japanese artist I listen to that I can only characterize as "coffeehouse jazz beat avant garde". Her name is
Ua (which makes her hard to search for
).
Then there's japanese ska (e.g.
Yum Yum Orange, etc)... and
Kotoko and her trance/techno music...
That '80s style crossover rock/pop girl band stuff (e.g. Zone, Scandal, etc)....
But then there's the never-ending Corporate Soft Pop machine that seems a softer version of "Z100" forgettable artist churn bleh. A fair amount of anime theme songs fall into this ear-mush category. It can get onerous picking through that for an occasional gem.
Of course, one can bop over to Enka or traditional folk and festival music but I don't think the OP is headed that way