From the book's introduction:
The term hikikomori refers to a phenomenon that’s become a problem in Japan, where adolescents and young adults (mostly but not entirely guys) start seeking social isolation, shying away from normal human contact as much as possible in favor of hiding in their rooms. Some of them have hobbies that keep them busy, while others just stare at the ceiling.
Jhonen Vasquez’ comic Jhonny The Homicidal Maniac probably played into this a little bit too, especially with the imaginary friends. Anyway, this game is a “solo RPG,” which admittedly is kind of an oxymoron. But I figured that if I’m going to make a game about antisocial shut-ins, it ought to be a game you could play by yourself. In this game you’ll be rolling dice (you’ll need plenty of ten-sided dice) and following instructions to generate events, making some choices about those and rolling a few more dice, and then writing a fictional diary entry based on the results. Out of necessity it’s not as open-ended as a normal RPG, but then it’s mostly a writing exercise. You can write on paper, type them up, or put them in a blog. Needless to say I’m curious what the results will be like, but you can do whatever you want with them.
By default, the game ends after your character goes through seven unusually eventful days. One of the ways in which it’s like a typical RPG is that there isn’t any particular way to “win.” If you want your character to get out of his rut and rejoin society, or stay the same, or kill himself, or whatever, you can try to steer him that way, but a lot of stuff will come down to how the dice fall. The real game is turning all this nonsense into coherent writing.