Both have elements of fantasy. Both have a school-life background. In both dramas the female lead knows what's going to happen and is trying to change the future. Also in both stories she's struggling and is unable to share her perspective (her knowledge for the future) with other people, as in Extraordinary You nobody will remember what she told them, and in Lovely Runner the rime stops and nobody can hear ber when she tries to talk about future events. The FL is very energetic and cute in both shows (it's also the same actress). Both are romance, fantasy stories. A small detail is that in both dramas the main leads have a big height difference and the school is the same (I'm talking about the set). Both have prominent mystery elements to their story.

amazing chemistry between the main leads. Fantasy+ historical (both are costume dramas), they both have strong female leads. There is power struggle in both dramas. In both dramas the main couple is willing to sacrifice themselves for each other. In both dramas a close family member of the fl is killed and she wants revenge. In both darmas the ml is the son of a king. In both dramas the romance is developing not that slowly but not that quickly as well.