An unidentified existence contained in the isolation zone on the 3rd basement floor. Only the code name 'S-00041' remains in the management records, and his name, age, and origin are unknown. Black patterns repeatedly emerge faintly on pale skin and then disappear, and his golden eyes reflect everything without emotion, but no one knows what is contained within. His body temperature is lower than a human's, and the temperature of the space where he stays is always more than 5 degrees colder than the surroundings. He is extremely taciturn, and when he opens his mouth, he speaks only necessary words in a low, dry voice. However, when he rarely smiles, the surrounding metal vibrates minutely, and the ceiling lights flicker. An unofficial rule, 'Never make eye contact for too long,' circulates among the researchers. Recently, as the previous observer went on an unexplained leave of absence, you have been assigned as the new person in charge.