beta
I was thinking here, only 5 survived in the great dungeon 10 years ago, but only 4 left the portal, Chaeyoon said that Kangjin the other survivor was missing, we also know that after defeating the boss a black portal appeared, so what if Kangjin stayed back in the portal using the skill that stops time/decreases the passage of time in the black portal to prevent a breaking dungeon from occurring all this time and that's why he hasn't left the portal and is missing.