High school student Ayumi falls to her death shortly after telling her friends, Satomi and Yuka, that her 'boyfriend' wants to kill her. The girls investigate her suicide and quickly link her death to a popular cellphone dating simulation game called Keitai Kareshi. The main features of the game include a 'love gauge' that determines how well the player is faring and the ability to trade boyfriends with other players. There is a rumour spreading that if the gauge hits either 100 or 0, you will die. Satomi insists on downloading Ayumi's boyfriend so they can interrogate him about her death...
