I really don't like the I-You POV and neither do many other people. Distances the readers n all that... but then this was for somebody, so maybe you should have changed it before posting.
You have indulged me this evening, as underneath you have on the underwear I presented to you earlier...
IMO, "...as underneath you have put on the underwear..." would read better. I had to read your sentence twice.
...remarking how wonderful it is just being together.
"...remarking on how..."
I compliment you (again) on how great you look and the desire it creates within me.
Why did you need the brackets for 'again'?
Similarly, you are excited by the sensation my emerging erection.
Lost an 'of' here.
As we enter the house, you kick off you shoes.
Just a teeny typo - 'your shoes'.
The paragraph starting with - As we enter the house... - seems too dry. I'd have liked more description of the feelings, thoughts and expressions of the characters. It reads like: I did this, you did that and we then did that too. As I went on reading, the same feeling goes on. It detracts from your sex scenes.
I commence to massage you body.
Another typo. you and yours.
What's a plasticube?
The beautifully obscene display beckons me irresistibly.
The use of the word 'obscene' jarred me. Maybe it's just me but this story is supposed to be hot, but essentially romantic and the word doesn't fit.
Your climax comes quickly, arms pulling at their binds...
Had he tied her arms? Where did I miss that?
I am but a stroke behind and me seed gushes forth
Typo #3: me / my.
Overall comments - The first half of the story was good and romantic, but you lost it somewhere in the middle.
I'd like to see this in third person.