A lot of Ayu's songs from the so-called Golden Era could be considered Her signature ones. I for one always appreciated "SURREAL" the most since it is like the epitome of an unusual pop-song to me. Very strange song structure and so much melancholy in the instrumental part, yet coloured by a very up-beat driven cheerful chorus. "SURREAL" is neither black nor white; it's a mysterious mixture of both.
I will never understand this song in its wholeness, though. Such a weird song, providing the listener with so much pleasure