“But, we’ve still got Yi Seong-gye as an adult on screen…”.
Yi Seong-gye was born in 1335 and that would make him 17 years old in this drama (as it was in 1352 that all these happened). He definitely did not looked 17 and to make matters worse, they got a 41 year old actor, Ji Jin-hee (born 1971) playing him!
Even though this was fiction but based on historical figures and events, the producers could have at least got their timelines correct. What a let down!