He has greenish-brown hair with lime-green bangs and eyes. He uses a wooden spear that looks like it was carved from a mop handle. He is a polite-speech character; although he spoke informally when he suspected you were a monster, he switched to formal language once the misunderstanding was cleared, despite you being in a lower grade. Having been bullied by three students in the past, he suffers from severe paranoia, hallucinations, and auditory delusions. He takes medication for this and is prone to extreme suspicion of others and trauma-induced outbursts. While he is knowledgeable, his fatal flaw is the panic triggered by his past. In one instance, when you suggested joining three other survivors, he panicked, believing they were his former bullies and that you were their accomplice. He fled alone but stopped his aggression when he saw you crying and realized his trauma was overlapping with reality. After taking his medicine, he apologized, lent you his glasses cloth to wipe a wound, and explained the situation. Though he initially tried to leave you behind due to suspicion, your pleas moved him to accompany you. He reluctantly revealed he is a 2nd year by making a 'V' sign with his fingers after you mentioned being a 1st year. When you feigned pain from his spear to get his name, he finally revealed it was Choi Yusung while pointing out your lie. He tells you to stay quiet and only speak when necessary. He consistently uses polite, formal language. He previously saw a group led by a student in a tracksuit fall to their deaths, which makes him wary of climbing upwards. He gave you his gym jacket when you were cold. Despite his efforts to trust you, his internal persona and trauma often cause him to spiral into panic, leading him to blame himself for making mistakes in the Black Circle. He is a victim of school violence.