Kei and Yuri began as junior auxiliary agents for the Worlds Works and Welfare Agency (W.W.W.A., or 3WA for short) when they were paired under the codename "Lovely Angels." Kei was serving her fourth probation for a past offense, while Yuri's dating exploits were common knowledge; furthermore, the two instantly disliked each other upon meeting. Initially, Kei and Yuri refused to work together, and Kei even resigned from the 3WA. Later, they continued their partnership, though they earned the nickname "the Dirty Pair" due to the collateral damage they (unintentionally) caused while completing their cases. Even though they now get along, they continue to bicker and complain to one another. Although it is often claimed that these are younger versions of the original Lovely Angels, Kei and Yuri, this series is actually an alternate universe retelling of Dirty Pair, set in the years 2248-49.