The current best-selling game is Square-Enix's Dragon Quest IX: Protectors of the Starry Sky (that's my translation of the title) for the Nintendo DS. A common joke is that Dragon Quest launch days are unofficial national holidays in Japan, as so many people skip work to buy and play the game.

Here is a DQ wi-fi access point outside of the massive Yodobashi Camera electronics store in Akihabara. I think you could download special in-game items or something.

I've never played a Dragon Quest game in my life. Though, I have been happily playing Chrono Trigger, which I bought for $20 the other day.