
iirc, seojun come to the script reading because it's his first time, not because he has a line in episode 1. The line he's saying about saving mother is not his line, why would he say it when he's the king 4th son? it's somebody else line, and seojun was confused with how different modern hangul and past hangul intonation(?), so Kim jongho who likes seojun say "you need to be more desperate here", correcting that somebody line while looking at seojun (but seojun just focused on the script writing anything that can help him acting better)
so other actors who's trying to get jongho help them with their lines become passionate, and everytime seojun confused, he will talk amd give some advice to those actors while seojun nodding and writing everything.
Is the artist not reading the novel poperly?