Yoshiko, a hardworking high-school student, is always taking care of others. Despite studying hard for herself, she still finds the time every day to copy her class notes and deliver them to her home bound, video game playing, childhood best friend who has not been to school for quite a while. One day on her way back from delivering the notes to her friend, she notices "black snow" falling from the sky. Confused, she asks her friends Miki and Kiriko if they had seen the snow, too. Having not seen anything, her friends assume she has been overworking herself.

Yoshiko, who also regularly helps out a reclusive uncle, one day brings her friends along to help, planning on doing some karaoke afterward. Due to the appearance of the black snow, an ominous event happens and things keep getting stranger and stranger…