They need to run ads, better yet, viral ones to post on Nico-nico-doga(the Japanese and more high-tech version of You-tube).
Suggestion: Get a bunch of junior & senior high school girls together (preferably cute ones), hand them all iPhones and let them play and text to their hearts' delight. Young females screeching, ahhing and giggling on screen is *definitely* the way to a Japanese consumer's heart (and his/her wallet). [Case in point, the Nintendo Wii commercials on TV and at their website where they showed all those families and friends having fun]
Also, iTS Japan sucks. Their music offerings are limited (many major labels are missing, most notably Sony), there are NO TV shows and NO Movie offerings other than Pixar short films. It's easier and cheaper to rent CDs and just rip those (albeit illegal).
The iPhone camera is also a disaster. Sharp and Toshiba and others have integrated great cameras into their cell phones which can also record lengthy video footage as long as you've got a decent sized mini-SD card handy. The music players aren't all that great and it takes forever to download a song even with 3G, as well as being very expensive even on an unlimited plan, so most people also carry an iPod (and/or other music player). Battery time can easily be lengthened on the run with AA portable battery chargers sold anywhere.
So it's not just emoji, TV availability and Japanese text input.
RE: amazon.jp, if you're going to pay at the 7/11, why not save yourself an extra trip and order at the 7/11 online store (http://www.711net.jp/). They'll email/text you a notice when your purchase arrives at your designated store and you just go in, show them the number (or you can print out a barcode if you really hate trees) pay and receive your DVDs on the spot.