Darker Than Black OVA 4 - This concludes the gap between S1 and S2, and does it hella well. Everything down to why Hei is like he is is now evident, and most of the plot holes are now filled. To be honest, this is what S2 should have been like, but there we go. Very much hoping that a S3 maybe announced for this at some point, and to be honest, i can't see why not. The DtB world is vast, so there is much they can do with it.