Where did you read the novel?
Do you know whats the deal with the woojoo hyung tho? Who is he?
Spoilers;;
That's js future yoogyul who fell off this cliff(if i remember correctly) in the same dungeon gyumin was trapped in that led him to travel back in time which explains why gyumin remembers woojoo hyung being older than him.
Ohhhh but didnt he say his voice was damaged, will be become mute after that too?
nono hes fine!!! he got emergency treatment right after :D
After readng the novel I was genuinely confused cus sm things were changed TT maybe like similar scenarios but different situations (if this makes sense sdgfyfj) I'm not saying this manhwa is bad cus manhwas are notoriously known for rushing the pacing and changing stuff, but the novel was just SO MUCH BETTER (in retrospect of character backstories and why they behave like that etc)（/TДT)/. Trust me, give the novel a try/;;