One day, Naho Takamiya receives letters that claim to be from herself ten years in the future, each letter describing a different day and what she must do to prevent her "biggest regret". At first, she thought it might just have been a prank but just as the letter described, Naho and her friends befriend the new transfer student named...

One day Lain Iwakura's class receives an email presumingly from one of their late classmates, after she had committed suicide. Usually she wouldn't even use the Wired network but suddenly she starts using the network, believing she would receive more messages even though everyone thought it was just a prank. Not long later, she...