|October 29, 2070|
|Shogo Makishima (former)|
|Unnamed sister (deceased)|
|0104 Nobody Knows Your Mask|
Gu-sung Choe is Makishima's friend and right hand man. He is an expert hacker, as he is able to breach through the security system of Sibyl's core and even witness its true form.
Choe has short straight brown hair that hangs over the right side of his face. His eyes are strange in that they appear to be both red and yellow in color; however, he usually keeps his eyes closed. He typically wears a blue jacket with a purple shirt underneath and green pants. He also has piercings on his right ear.
Choe is a scientific genius and the one responsible for spreading rumors around the internet, causing chaos for a while. He, like Makishima, wants to see the Sibyl System dismantled. He cares not for others and has no problem with people dying, as long as it furthers his goals. Ironically, he sometimes shows that he can only take blood and gore to a certain extent, as is seen when he leaves Rikako Oryo to dissect her victim alone, since he doesn't want to witness it.
As a child, Choe flees with his family to Japan because there's war in his homeland, Korea. In corrolation with a statement in the episode, this may have happened in 2097 as according to a satement he made, he has been researching the Sibyl System for five years.
Eventually his eyes are damaged for some reason and have to be replaced by artificial ones to save his life.
Around 2111, Choe meets Makishima for the first time; therefore, doesn't know about Kozaburo Toma.
Before being sent to Japan for a mission around 2097, Choe works for the Korean military force, specializing in sabotage jobs and cyber warfare. Korea is destroyed during the war.
After wandering aimlessly for ten years after the destruction of his homeland, Choe becomes an acquaintance of Makishima around 2107.
Choe is Makishima's right-hand man and the closest thing to a friend the man knows; and despite of what Makishima has done, Choe sticks around, serving as Makishima's messenger between "the client" and Makishima.
- Choe Gu-sung's name in Korean is written as 최구성 (Revised-Romanization of Korean: Choi Gu Seong).
|Shogo Makishima - Gu-sung Choe|
|Rikako Oryo - Toyohisa Senguji|
|Kirito Kamui - Mizue Shisui - Sakuya Togane - Misako Togane|
|Nicholas Wong - Desmond Rutaganda - Yulya Hanchikova - Jean Phillip Weber - Babangida - Bun|