Responses
It's likely that there are multiple candidates for FL in the original novel. One is a student around the same age as the original MC and 2nd MC while the other FL is Sejin. It's already mentioned the Sejin and original MC fall in love in the book. I guess then it's likely that the other FL is paired with the 2nd MC.
W8 when he was talking Seora out of Antas,he mentioned the fl's parents died from a car accident on antas's mission,but here he is saying that Sejin is the fl??