I liked the dynamic between the two leads. I like it when the power dynamic is "reversed" i,e, not based on gender roles, and I like the devotion the characters show each other. They are very observant of each other and I have never seen a show/person better at recognizing someone's strengths and portraying them in a cool, upfront, and selfless way.
Of course, while this stems from a good (if standard) story line, it is the acting of the Male Lead that puts this show at the top. He brings out the best in the plot and in the characterization. I can go on, but one thing that really stuck out to me was that in so many East Asian dramas, the male lead catches the female lead when she trips or something, but in this one, it's the female lead that does!!! I LOVE IT. The gender police's sirens aren't going off. She's not a bulked up warrior, she doesn't have to be! You don't have to be as strong as a man to catch someone in your arms! Or trap them up against the wall with your hands bracketing either side of your face. There doesn't have to be a reversal of gender roles because it's cute and hot and it makes the audience's (and hopefully the male lead's heart go doki doki even more! It rejuvenates an overused plot point, it puts characters on a more equal footing, it adds depth to the possibilities that this genre can offer and the twists and the cute scenes this drama can take! It's so fun and beautiful.