I have not seen the YnM anime, but the manga is one of my favourite series. The art is gorgeous and it's hard not to love (almost) every character. The manga's been licensed by Viz, so scanlations may begin to disappear from the net. I wish I could recommend a place to buy from, but the only thing I can think of is to check ebay for those who might be selling a whole set used. (Why anyone would want to, I have no idea!) Or, if you or someone you know can navigate it, Amazon.co.jp. Yen price and not-horrible shipping (usually). Or, someone in a city with a Kinokuniya or Asahiya might be able to look for them for you.

There has been a lot of yaoi (I think mostly referred to as "BL" for Boys' Love in Japan now) with explicit artwork in recent years. I have no idea what those titles might be, but you might want to check out Aestheticism.com for your general, er, yaoi-knowledge furtherance?

(I am a perpetual source of half-assed information, I'm sorry. I just felt my fangirl YnM squee returning to me after months of sadly coming to the realisation that I was never going to see a volume twelve. *sigh*)