Error the Echo

If one dies in this horror game, death also occurs in reality. However, I am the only survivor.
Characters:
Gu Hyeon-Seung
is the main character. He suffered from a spinal injury when he was 14 years old and cannot feel his legs anymore. He played the online game Dark City until it was closed down and feels hopeless after that. Suicidal thoughts are also consuming him until he receives a message from his father Gu Gyeong-Hwan who tells him to play a different game.
Celine
is one of the characters in the Dark City game who Gu Hyeon-Seung liked. Unfortunately, after Dark City was shut down, she could not be seen anymore.
Gu Gyeong-Hwan
is a father of Gu Hyeon-Seung. His whereabouts are unknown for more than five years, but suddenly he sends his son a message saying that he has created a very special game for him and urges him to come to the company that he has mentioned.
 
CEO Im
is the representative of the company that Gu Hyeon-hwan asked Gu Hyeon-seung to join. Unlike the other employees, he knows Gu Hyeon-hwan, and when Gu Hyeon-seung arrives, he introduces him to a virtual reality game that Gu Hyeon-hwan created.