What a sweet story! I enjoyed watching their relationship develope. I love your mature Harry, it's a nice change from clueless!Harry or whiny!Harry. Also I really love this line.
He wanted to go hard and fast and slow and sensual and everything in between.
And I loved the mild overtones of D/s. This part in particular is just beautifully done.
“There is a strength in that, something which few others understand.” Severus remained silent, but gracefully dropped to his knees