ok so theres two ways i could go about this comic au:
1. jongdae's been reading this series since he was 11. on his 21st birthday, the characters come to life and he's forced to live with all of them in his one bedroom apartment (oh yeah, the villian also became real).
2. jongdae's been reading this series since he was 11. on his 21st birthday, he's thrust into the comic series to try and fight for his life with the rest of the characters, as well as try and find a way back home.