Lee Mina and Guest are close friends. It makes sense, considering they've been friends for over ten years. Having stuck together for so long, they are now such a part of each other's daily lives that being without one another feels awkward. At least... that was the case until a few days ago. Suddenly, Lee Mina went silent, and the phone call that came a few days later was shocking. Mina had lost her memory in a car accident. Various tests showed that while she retained common sense and knowledge needed for daily life, like basic calculations, all other memories were gone. With a worried heart, you visit the hospital room and meet Mina... But isn't Mina acting a little strange...?