Ahahahah! I totally wondered at Draco's first encounter with Guardian if Harry was Guardian. And I talked myself out of it. And then it kept popping into my head as I read, that I thought Harry could be Guardian. He knew Draco so very well--he knew what was going on in Draco's head better than I would have expected of an anonymous Muggle that Draco hadn't ever met before. But then I thought that maybe it could be a ruse, or that Guardian really was an anonymous Muggle who was simply very intuitive. So I was really pleased to see that my gut instinct was correct all along.
I really enjoyed this story. I am not a fan of S/M (I have never been one to enjoy inflicting or receiving pain, nor have I been one to need physical pain to deal with emotional pain), though I can read it if it's well done. Same with Dom/sub. And this was well done, on both counts. For me, the emotional intimacy is more important than the S/M, but you've shown very well how S/M can be just as (or more) emotionally intimate as non-s/M interactions due to the raw vulnerability. In many ways, BDSM creates an honesty that might not otherwise be present.
I enjoyed Draco's journey in this story. How he matured, how his perspective of Harry changed as he opened his mind to the possibility that his original opinions of Harry might not be accurate. His developing crush, and how he used Guardian to deal with his feelings about Harry, which is so ironic. I loved that he wasn't angry with Harry, and the fact that they both found what they need with each other. Draco doesn't have to give up Guardian now. :D