In 1999, while the world is gripped by the Y2K scare, identical twin sisters “You” and “Me” are also concerned for their future. The twins are so close with one another to the point that they share every aspect of life with each other.

One day, a boy named “Mark” comes into their lives. When the twins are confronted with their “first loves which are not shareable” unlike everything else, how will this internal conflict lead the twins into a new phase of their life?