The songs is amazing. The beginning starts with it's softer piano, and Taemin's voice in the appearance of little humms. Then his voice comes, almost strong, to a soft background that creates a sorrowful, but powerful atmosphere. Then comes the chorus, with the dubstep breakdown, which I always thought sounded like laser guns in music. All the contrasts in the song send me on a rollercoaster every time. His ad libs in the song add so much, and really fit in. And that last goodbye, a sudden end, but fitting right into the theme wraps it up quickly.
I don't know why, but I get a really intense feeling listening to it, a sad sort of longing lingering in my chest, and I think it's really good. Plus the music video is mysterious and magical, with the dancing on the piano, the flowers, the lava. Taemin looks like an anime character too.