First can I say that Invisibility sex is a total kink of mine. Yummy!!! I think you're enjoying writing Snack, and I'm enjoying reading it!
And in true Nishi style, your endings tug at my heart strings for our tragic Severus. Your endings always have some of the most beautifully arranged words ever written. It started with: "There is no us." And just continued to get more amazing.
(ok ... gotta get ready to go to work ... thanks for the great start to the day!)