A middle school student named Kozue finds a red balloon with an SD card attached to it. On the SD card is an invitation to the wedding of two complete strangers. In order to escape her daily doldrums, Kozue decides to go to the wedding with her classmate, Kikuchi. However, along the way they cross paths with a pair of suspicious men, a mysterious girl, and a strange cop. When they finally make it to wedding, they get drawn into the fray of yet another unexpected situation.