This is my fourth favori Honeyworks song as well as one of my favori Rin and Len duets so far. Classic. It's an old one with some poor tuning, but the song itself has really shaped the VOCALOID industry and its personification of the libraries.
This is one of my favori Regulus songs as well as one of my favori Megurine Luka songs. I remember listening to this just a few hours after it was released.