Recently, a mobile game called "Mobile Boyfriend" has become popular among female high school students. In the game, girls can choose boys with different images as their virtual boyfriends according to their preferences, and enhance their relationship with them through key operations. Mayumi Nagauchi (played by Miki Nakagawa) is a heavy fan of this game. For her, the handsome boy in the mobile phone has long surpassed the virtual image and has become an indispensable part of life. However, from now on, Mayumi will never see her deeply infatuated virtual boyfriend again because she is dead. The message left by Mayumi before her death suggests that this tragedy is inextricably linked to "Mobile Boyfriend". In order to find out the real cause of death of her friend and the truth of the incident, Ueno Satomi (played by Kawashima Umika) and Onodera Yuka (played by Asakura Aki) and others launched an investigation into the incident.