A teenage girl named Monica has been training all her life to carry on her family's deadly assassin heritage. Her first assignment is to go after the Dirty Pair. Kei and Yuri go to a vacation resort to relax but soon find themselves on the guard as bombs, traps, and deadly attacks appear wherever they go.

Kei discovers that Yuri is hanging out with a young teenager, and goes over to them to give Yuri a slap on the back, but Yuri's head falls off! It turns out the boy had created a life-size android of his crush, Yuri! Oops! Kei apologizes, but the 3WA wants more than an apology. While the android is being repaired, Yuri is ordered to take the place of her look-alike. Yuri protests until she learns that the boy is part of an extremely wealthy and influential family that even funds the 3WA. This is Yuri's big chance to finally date and marry rich, and the boy's chance to be with the real Yuri! But the boy only cares about his Yuri's ideal traits of being sweet and innocent, and shuns the realistic ones that she and every girl have. Can Yuri win him over without losing herself in the process?