As we've discussed, your choices for print versions of your favorite American mainstream and smaller-press comics in Japan are very limited. As in almost non-existent. You can find some online retailers and pay massive shipping costs or you can buy digitally. The latter is what I've settled on doing through Comixology and, to a lesser extent, the also nifty Dark Horse online store.
While I don't mean to shill for Comixology-- not being able to download your comics to read them offline is a major irritant I have with them, after all-- or for Dark Horse-- same deal-- as a comic fan in Japan, those are really the only games in town. Strangely enough, after years of accumulating actual hold-in-your-hand comic magazines stored in the classic "longbox," I now have the most extensive comic book collection of my life in digital form. I own comics I could only dream about having-- key books from the Golden Age, almost three dozen Fantastic Fours by Stan Lee and Jack Kirby, complete runs of favorite titles from my childhood and teenage years plus a scattering of random choices from some newer offerings. And even though I'm not a supporter of what Marvel and DC are doing these days, I am buying a few individual issues just to keep up with developments or because I like a particular character or other.
Dani Moonstar and Katana, I'm looking at you!
I haven't spent as much money at Dark Horse, but there's no reason for that beyond my obsession with books like Kamandi and The Walking Dead, which you can only buy from Comixology. Eventually I'll hit Dark Horse up for all the Hellboy and Conan titles they carry, plus those Creepy and Eerie collections I love. In the meantime, Comixology also offers IDW and Fantagraphics products, Image, The Rude Dude Productions Nexus issues and their new self-submission titles, some of which are worth reading.
If you're living here in Japan and you're interested, you need to check out both Comixology and Dark Horse.