This is the mode of the game which uses Streetpass. If you carry your 3DS while it's in sleep mode, it will be able to tag other Super Smash Bros players and get their character tokens. The gameplay is simple. Using your own character token on the stage, you have to attack and push the other token offstage. You can use the dash attack by pressing A. Press and hold to charge and unleash a powerful dash. Knock out more opponents to get better prizes.
Before you start the session, you'll see the list of people you tagged and their Street Smash stats.
You can also modify your Street Smash profile by selecting your preferred character token and even setting up a personalized greeting.