The stories take place in the years 2138-43, by which time humanity has spread across some few thousand star systems. A corporation called the World Welfare Works Association (also WWWA or 3WA) helps member systems of the United Galactica (UG) federation deal with various planetary-scale problems, for profit, by sending agents called "trouble consultants". Probably the most high-profile arm of the organization is the Criminal Investigations section, which works to solve crimes or mysteries. The series focuses on a team of trouble consultants in that section, named Kei and Yuri, who have a reputation for leaving a trail of destruction behind them, for which they are known publicly as the "Dirty Pair".