Swapnote, the new app for the 3DS that lets folks send 3D messages to their friends via SpotPass and StreetPass, has hit the U.S. Nintendo eShop today. First announced back in October, the app is entirely free, and sounds like a good way to harass stay connected with enemies friends by way of horribly-offensive thoughtfully-crafted personal messages.

As noted by news site Tiny Cartridge, the application features a guide named Nikki (the Japanese translation of "Diary"), who apparently gives you helpful advice about... writing notes, I suppose. The Japanese version of Swapnote, released yesterday is called 'Itsuno ma ni Koukan Nikki.'

In any event, you can check her out in action in the Japanese trailer for Swapnote, below.