This game represents everything streetpass was about: The connectivity with other people in your neighborhood who also had a 3ds, the fun of seeing the Mii of your friend slay a ghost, the excitement to see the green light... Dear God, that green light. I took my 3ds out every single day back then, just to have a chance to even see that thing turn on.
And it felt glorious when it did.
This game would not stand up on its own if it weren't for it's community: YOUR community. Combat is not that fun.
It was special because the people around you made it special, and I'm afraid we won't be seeing anything like it in a long time.
Thankfully Netpass helps with it, but it's still not the same. Perhaps another time...