Ai (Jeong Hae-yeon & Hyeongeom)

A pharmaceutical company started to secretly develop a new drug. The new drug's goal was to prevent humans from aging. They finally succeeded in developing the new drug after three years of research, but it couldn't be trusted without a clinical trial. Eventually, the researchers began testing the drug on people of unknown status illegally. As a result, 12 of the 20 subjects lost their body rhythm within a week and no longer aged. However, as the researchers became eager to report the findings, an unexpected change in the subjects' bodies began.