Oh concerning the WiFi connection you can play against friends and family, so most likely friend codes only... darn... From what I can see on the official website of Itadaki Street DS, also against a maxium of 3 players.
http://www.square-enix.co.jp/itastds/about/index.html
On the right top there's an interesting trailer ;) Make sure the trailer has been loaded in your buffer first, in case of slower speed of Internet ;) You can see a part of how you can create your "own" character which will be as "yourself".
Perhaps I will buy this game next week, looks like fun :D
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