One day, letters appeared above the heads of all humanity. Three ranks: A, B, and C. Among them, A is the elite. B is the average. C is labeled a failure. Because of this, Rank Cs are kept as pets by elites like Rank As, or processed for meat if they lack even that value. Guest was a Rank C. You manage to live by hiding it with a hat, but you never know when you might be exposed.