Japan are my favourite band (ever since playing my older stepbrother's 12 of Life in Tokyo to death and progressing from there aged around 13 in 1984, so I never saw them live but caught Sylvian at Manchester Apollo in about 1988/89), but it's eye(/ear)-opening to listen to
Out of the Blue off
Country Life (a lyric on
Gentlemen Take Polaroids, of course) and much of
Manifesto to hear very very clear precedents for the Quiet Life/Polaroids sound. Seriously have a listen to the opening of
Out of the Blue - from what, 1974?
While no one would call either
Country Life or
Manifesto "glam", the point that Japan are not new romantic is fair, but that Duran Duran are a poppier pastiche of Japan is indisputable, down to their look, poor old Nick Rhodes continued with the David Sylvian Polaroids look well until...now..? You have to hand it to Duran though - they weren't manufactured, had stratospheric success and I'm not ashamed to say I loved many of their songs then and now. Plus
Rio will get people going at a party in a way that, sadly,
Methods of Dance will draw a blank
They even copied the po-faced existential Euro-art Japan of
Nightporter - with e.g.
The Chauffeur (love the ham-fisted stab at finding a profession with similar metaphoric potential, B&H and Carling vs. Gitanes and Ricard).
It's daft that Sylvian disowned the early Japan, because as the OP was inspired to write, Adolescent Sex is great. But, like Duran after them, unabashed pastiche - of the New York Dolls (
ahem, Sylvain Sylvain), down to the look. In the service of something new and nothing wrong with it, it's not as if too many other were influenced by the Dolls (BBC OGWT Simpering Bob Harris: "mock rock").
And to the playing - some bands just gel don't they? All from Catford area, two brothers, into same music, probably jammed for hours (clocking up Gladwell's 10,000 in their teens), singular purpose. But the era of "non-musicians" produced many incredible units, e.g. Magazine.