As a replacement for the mysteriously missing Akiho Yoshizawa, Ai, her former junior and close friend, arrives at a small hospital to work as a nurse. Her true purpose in taking the position is to uncover the truth behind Akiho's disappearance. While carrying out her daily duties, Ai begins to notice strange undertones in the hospital's atmosphere and the hidden secrets behind the patients, gradually drawing closer to the truth. A suspenseful story of Ai's investigation into the enigmatic hospital.