I'm fairly comfortable calling this "YA psychological fiction," although the truly suspenseful stuff doesn't start to come up until halfway through the book.
Synopsis:
Sawako is a fairly ordinary, if socially withdrawn, 13-year old. One day she gets an email from Yukari, a girl she has never met, inviting her to take part in the creation of a fictional world. By this, Yukari means that she, Sawako, and two other teenagers will write a joint story. Yukari sets up the basic premise and defines the four main characters. The story will be about a teenager who is being stalked. The four main characters are the teenage girl, her tutor (a college student who is either the object of the teenage girl's affection or already her boyfriend), the stalker, and the woman detective who pursues the stalker. Sawako chooses the part of the teenage girl. Yukari has already chosen the part of the stalker. Other girls receive the email, forwarded by Sawako. Mai, a lonely girl with wealthy parents, takes on the role of the tutor. Mayumi, a girl who lives in her badminton star friend's shadow, takes on the role of the woman detective.
As the writing gets underway, all the girls are excited, staying involved to the point that it sometimes interferes with their daily lives. In an effort to keep their writing good and realistic, some of the girls naturally incorporate aspects of their lives into their writing, unintentionally allowing the other girls to start to get to know their real selves. Then something happens to Sawako, and Mai and Mayumi are worried when they realize that Sawako's latest post may indicate that she is scared and being stalked in real life. Then she disappears for four days.
Up to this point, everything these girls know about each other they have to guess using details gleaned from their joint story. If any of the girls purposefully meet each other or talk to each other outside of the story, they are essentially breaking the rules of their arrangement. However, Mayumi becomes concerned enough about Sawako that she decides to contact Mai, making arrangements via her detective character in the story. When Sawako begins writing her part of the story again, however, further arrangements prove to be unnecessary.
Except that things only appear to have gone back to the way they were before. What really happened to Sawako when she disappeared? As Mai becomes more curious about Sawako and tries to learn more about her without breaking the group's rules, there are indications that it is now Mayumi who's in danger and that things are not all as they appear.
