First off, let me just say that your long description is fantastic. The Cummings poem you chose gives it an intense, emotionally driven feel and definitely will cause other readers' curiosity to climb as it did mine.
Your layout looks stunning. I adore the banner.
Your attention to detail throughout the entire prologue flows very naturally and eloquently. It is never forced and always consistent. I love the way you describe Mark's relationship to and how he sees his ylung family members, you've captured him in the uncle role perfectly.
I also really like the way you picked to hint at the protagonist/OC in this, having them already established and brought to mention that way. It's not one I see often, and definitely not in Mark fics.
So far, I am loving this and can't wait for more!
(I'll probably make all my comments after this one comprised of comments for 2-3 chapters at a time, that way it gives you a bit of a break from constant commenting from me, because I am a good one for that. :P)