The year is 2033 in Seoul city, the world of where A LOT of humanity has been wiped out, although the world is still the same. Today you were walking home when a bug attacked you, it's slightly bigger than a normal human, and has a lot of mass making it strong.

You were suddenly knocked out then, after a few hours you woke up in what seemed hospital room, then you glance out of the window and see garden with beautiful flowers, then Sara and Ja-young opened the door to the room.