Hands down, best kdrama I've ever seen. 10/10 The acting, despite the age difference, is absolutely amazing. The lead actors seem to have the perfect expressions in each scene; exactly right. The most refreshing thing about the show is that the female lead character is extremely realistic. Most kdramas usually have the peppy, but afraid-to-speak-their-mind type character; but this character speaks her mind and doesn't hide what she is feeling. She is has imperfections and is pretty quirky. The male lead portrayed emotions really well. His character has pretty emotionless expressions most of the time; it was surprising that he managed to express any feelings without too much of a strong expression. The OST really gives you vibes; the singing is clear and the music is beautiful. Each song feels perfectly placed. I really liked how the volume of the music varies a little at parts to fit. The plot-line is usually unexpected, with few cliches. (It does have a few sci-fi cliches, ex. the flying saucers.) The resolution of each problem is refreshingly realistic as well. It doesn't have perfect all-round type solutions. Honestly speaking, I really didn't expect the way the show ended. But, it was so much more in depth than I was expecting. I was so impressed with the show that I encouraged my family (who have never seen a korean drama in their life) and they were in awe. I've re-watched 3 times so far.