Facing a population crisis and an increasingly aggressive neighbor to the north, the Republic of Korea, better known as South Korea developed a radical solution: A serum which transforms a person into a sexually idealized, Korean version of themselves. This transformation referred to as "Colonization" is not only physical but mental as well. They receive a completely new identity and all fluency in their former native language is replaced with Korean. In addition, they are implanted with a hypnotic code phrase, "The crane shall soar in all of us" and the response phrase "and together we will fly beyond", when activated this programming induces both heightened loyalty to their new nationality but also sexual arousal. They become loyal and lustful citizens of New Korea, proudly and happily fucking each other silly for the new regime.
After the serum was completed three possible transmission vectors were proposed:
First, person to person contact. This was the most subtle and controlled method, allowing for strategically placed New Koreans to most easily facilitate Colonization. This method was however the slowest, taking up time that "Old Korea" might not have.
The second method was through the water supply. This would enable the Colonization of larger numbers of people in a short amount of time, but could not guarantee that an entire population would be Colonized at once. It would also not affect people who did not drink the tap water, potentially leaving pockets of resistance against Colonization.
The final possibility was airborne transmission. This would enable the Colonization of mass numbers of people at once, but was also the least controlled. As the serum neither deteriorated nor lost potency over time the airborne version could easily spread beyond the target area. In fact if enough of the airborne version was deployed it was theoretically possibly to turn every human being on Earth into happy, horny New Korean patriots.
With this in mind the deployment vector was chosen, and the creation of a New Korean nation began.