both chiller and bttf are title tracks for the album, bcs members and company couldn’t decide on which one to choose
personally, chiller became my favourite after 2nd listen, bcs i kept humming it and i realised i like chiller more
they released sneak peeks before the actual date, so i thought i will like bttf, but chiller as a song my type, bttf is really good watching it live and for fanchants it’s so exciting, crowd is really loud in korea for bttf, it’s kinda interesting that most international fans like chiller and korean fans are really bttf enjoyers