Episode #1.9 - S1-E9
Continuity mistake: When Eugene stabs the sword through Se-hun's chair and slices the side of his neck, there is a blood stain on Se-hun's collar. In the first shot of Se-hun after the sword goes through, there are three or four tiny blood streaks shown along with the stain. For the following ten seconds, the tiny blood streaks disappear, only to suddenly reappear. (00:56:03)