It's not just the leads but there's great chemistry for the whole cast, yes even the teachers. This touched me in ways I didn't expect and maybe one of my most favorite HS drama.

There's the typical bickering, skipping classes, love triangles, secret crushes, etc. The usual teenage drama. At first l, I found the FL to be too loud, too smiley, eager to please and quite annoying. This feeling did not stay too long as the FL continued to show her sincerity to her classmates. What I didn't expect was the depth of her insecurity shown in this drama. When the description said that the FL's negative feelings exploded, I thought it was an exaggeration but it wasn't. She really did explode and I cried when she did. That was probably one of the most powerful scenes in this drama because the FL's reaction and actions after that scene was sensitively shown and handled.

As for the love triangle, I was totally onboard on whoever the FL chose because both the ML and SML were great guys who have sincere feelings for the FL. Both had chemistry with her too. Actually for most of the story, the ML was acting like the typical second lead. He was fun, usually gives advice to the FL but was never really noticed. He was eclipsed by the SML who is like the typical ML, clueless about love, sincere and good at everything. The way this triangle finally moved forward was shown with so much heart and understanding.