This is a mature NC17 story with an Ichigo x Kisuke pairing. It's a post-war story, where Ichigo is trying to pick up the pieces of his life and figure out where he belongs. He is not a shinigami, and would never be a part of that structure, but he also can't just push the war behind him and 'play pretend with the humans'. Ichigo realizes that what he's doing is not working, so he seeks to do something different. He begins a relationship with Kisuke. He is well aware that this relationship is not based on love, and that it is not going to fix his problems, but what it will do is give him some stability as he tries to figure out where he stands in between Soul Society and the Ningenkai.

While Ichigo is actively trying to find his place, his father Isshin is desperately trying to shield his son from the aftereffects of a war he didn't participate in. While his heart is seemingly in the right place (I can understand where he's coming from, but I really just want to smack him), he is only pushing Ichigo closer to the edge. He is only alienating Ichigo and Karin as he tries to 'make things right'.

This is a supremely well written story, one that I would recommend to those of a mature mind and tolerant attitude. It brings up some very nice points on the aftereffects of war, and an interesting perspective on some characters and their actions and pasts. There is a lot of discussed character death (they did just finish a war), and a good amount of sex between Ichigo and Kisuke, but it is tastefully written and even serves a purpose.

This story also comes with a prequel, called Falling into Darkness. You can easily read Shades of Grey without it (seeing as how I found it after I had finished Shades of Grey), but it depicts how Ichigo and Kisuke stumbled into being lovers. It lies down some background material, but is really a glorified PWP.