Highschool miniseries starring Jung Da Bin.
Her character has a secret to hide, where she's going through tough shit.
Both the dramas revolve around Korean highschool kids.

The chemistry between the three leads looks so much similar to Cha Eun Sang, Kim Tan and Choi Young Do. Even some of the scenes in the trailer have a lot of resemblance.

Probably different plots, but, structured around the school life of three teens caught in the web of a love triangle. So yes similarities are bound to happen.

Okay, so the plot obviously varies. But, in short, I find them similar because of the love triangle. And, how the two male leads have constant fights for the female lead. The second lead in Extraordinary you will often remind you of Choi Young Do (after like 6-7 episodes, till the plot unfolds layer by layer), so, the second lead syndrome is real, bro.
Gives off a similar vibe.
One thing you should know is that Extraordinary You is low-key a satire of typical Korean Romantic comedies, like, let's say Boys over flowers, or The Heirs itself. Yet, as the story proceeds, you start seeing SOME of the cliché Rom-com stuff (like a love triangle and etc) blossom among the main characters of the show (not the comic in the show), which is ironic.