Wikipedia
Swapnote
Swapnote, known as Nintendo Letter Box in PAL regions and Itsu no Ma ni Kōkan Nikki in Japan, is a messaging application for the Nintendo 3DS family. Swapnote was released on December 21, 2011 in Japan and December 22, 2011 in Europe, Australia and North America via the Nintendo eShop. It can be downloaded at no additional cost and is pre-installed on newer systems. Swapnote is the successor to the PictoChat app for the Nintendo DS line.