.hack//Infection, .hack//Mutation, .hack//Outbreak, and .hack//Quarantine. These four games are each "chapters" of one massive game on the Playstation 2, sometimes collectively referred to as ".hack//IMOQ". They take place immediately after .hack//Sign, and form the core of the R1 storyline of the .hack saga. .hack//Liminality takes place concurrent to the games' story. See here for character sheets.