Haven't seen an odd creature is living its life overlapping with human, not supernaturally but the creature that mostly fit to explain biologically? I suggest you to watch this one, Kiseijuu: Sei no Kakuritsu [寄生獣: セイの格率/ Parasyte -the maxim-]. The original story comes from an old manga, started on 1988 and ended on late nineties. The feeling of old manga is still there, but obviously the show that ran on Fall 2014 - Winter 2015 (24 eps) is worth trying as its animation is done nicely by Studio Madhouse.
【Download the theme songs here ♪♩♫♬】