A Weird Copy That Starts with Hearing Emotions

That was a strange letter. Gu Jin only knew that from that day on, his life changed. This place is called the rooftop... A ​​place where reality does not exist. The only thing a challenger who is accidentally involved in is to abide by the rules and complete the task. Failure means death… And... What kind of unknown secret is hidden behind this anomaly... This is a trial that tests humanity and survival. Grasping all the clues and keys is the key to victory. (Good luck, challenger...)