Kei and Yuri were originally junior auxiliary agents in the Worlds Works and Welfare Agency (W.W.W.A. or 3WA for short) when the two were paired together under the codename "Lovely Angels." Kei was coming off her fourth probation for something she had done, and Yuri's dating exploits were common knowledge, not to mention the two had an instant dislike for each other when they met.
At first, Kei and Yuri refused to work with each other, and Kei even resigned from the 3WA. Afterwards, the two continued to work together, although they earned their nickname, "the Dirty Pair" because of all the collateral damage the two (unintentionally) cause in the completion of their cases. And even though the two now get along with one another, they continue to bicker and complain to each other.
Although it is often said that these are younger versions of the original Lovely Angels Kei and Yuri, in truth this series is an alternate universe telling of Dirty Pair, set in the years 2248-49.
Dirty Pair Flash is a re-imagining of the Dirty Pair franchise. As it is made more recently they've beefed up the animation budget and the animation is of a far superior quality to the other Dirty Pair OVAs and movies. The sound has improved too, except that the quality of the english voice acting is still a little bit lacking. Alas, the opening theme sounds like kindergarden kids trying to sing to really bad 70s porn soundtrack. At least that's how it sounds to me.
The stories are quite good and varied. Mission 1, the first 6 OVAs is one central plotline, as is Mission 2
with 5 episodes. Misson 3 is a collection of random episodes. Mission 1 was quite annoying and dealt with the relationship between Kei and Yuri. Mission 2 was the best in terms of a cohesive storyline. Mission 3 is just fun, funny and features 2 boob shots.
The real issue with Dirty Pair Flash is the re-set of the characters. They made both Kei and Yuri younger and very immature. Both are now 3WA agents that are great physical specimens with good combat scores and extremely low IQs. WHAT???!
What happened to Yuri being the smart one as per the previous Dirty Pair? Now all she is interested in is clothes, boys and telling the world how cute and pretty she is. Definately not much interest in the job. The beefed up Kei is now a total tomboy in love with guns, who happens to have the IQ of an egg. I understand the "old" Dirty Pair was reckless but making them reckless bimbos is a bit much.
Overall, the stories are ok, the action is good, the animation is better, sound is so-so. In addition there is a lot of semi-nudity and eye candy for the ecchi guys to look at. I really wanted to enjoy this series more but the incongruity of how the characters were made killed a lot of it for me.