In the future, the DNA inside people's bodies can be altered, thus changing the person themselves. Such people who are able to do such things are called DNA operators. Karin is the best DNA operator of her time. By the use of her DCM bullets, she shoots her patient with a gun-like mechanism and introduces or removes certain DNA. In a special assignment, Karin is sent to the past to eliminate the Megaplayboy -- a man who was able to get 100 women pregnant. And of those children who are boys, they also get another 100 women pregnant, and then so on and so on. The reason for this assignment is due to an overpopulation problem in the future. Having more than 2 children is now a crime punishable by death. Therfore, the Megaplayboy is a huge problem. But since the original Megaplayboy was dead by her time, Karin must go to the past and stop the Megaplayboy by changing his DNA. For a reward, the government has promised to pay her so she can have a nice house, a kawaii (cute) pet, and a husband (of which she still has to find). From her records, the Megaplayboy is a teenager by the name of Momonari Junta. After following him around for a while, she is able to shoot Junta with the bullet. However, as she prepares to return home, she receives a message from her boss saying she took the wrong bullet. After calculating the ramifications of her mistake, she discovers that she in fact created the Megaplayboy by shooting Junta with the wrong bullet. Fortunately, the Megaplayboy DNA did not become stable and Junta fluctuates from being the Megaplayboy and himself. So now Karin is ordered to observe him and make sure he doesn't change into the Megaplayboy.