From the introduction:
This book contains the rules to take the worlds you've created with Inuma and do something fun with them. You're going to make a story, but you're also going to play a game, but there's not going to be a score and no one's going to lose. As you can see, this activity is not easy to define. It is what it is. We call it "story gaming."
You'll need two to five friends to story game. It will take between one and three hours, depending on how many people are involved. What you're going to do is create a short story that can be tied together with other short stories to weave an epic involving the world you've created.
Generally, everyone playing will have the same things to do, but sometimes the "host" will have special duties. This is usually the person who invited everyone to play a story game or the person who owns the Inuma set, but it can be anyone you designate.
The Yellow Book focuses on cooperatively creating and detailing the significant characters for the campaign. Unlike traditional games, in Inuma characters are cooperatively shared among all players.