Kurogane Communication - episodes 17 to 24

Kurogane Communication pulls it all off for the grand finale and even promotes a few tears.

These eight episodes feature with the other "only human left on Earth" at the fore. While Haruka is a good character, Kanato has had a much harder life. This makes it excellent for the two of them to interact. Kanato is not simply a character whose rude exterior hides a heart of gold, but rather a character who has had his heart of gold tarnished and needs to understand many things that have not been available to him due to his different, cold upbringing.
So the last third of the series is about their relationship and coming to some sort of agreement about choosing to accept others. There are some great cliffhangers, some good feelings of pain, and a couple more of the really creepy scenes driven by literal thinking.
To say much more would be spoiling, and that wouldn't be fun - this is a very well developed series that eventually got to use all of its characters and more.

The artistry involved in the making of this show was quite amazing. There are moments of fluidity where one might not have expected them, and there is some creative visualisation. Kanato's nightmare is particularly impressive, particularly with its contrasts to reality, and so too is one of the most emotional monologues in the series (delivered by Sakuma Rei) conveyed perfectly.
There are a few low-budget gags along the lines of sweatdrops, that are kind of out of place among the general straight nature of the rest of the material, but they do not detract from any enjoyment.

Kurogane Communication is a big surprise of an anime, and that is a huge part of its appeal - coming into it, it still feels like something you've not seen before, even if you think you know what to expect.