Ok, first of all...her name is not Bunny, its Usagi. :P I know Usagi 
means Bunny but arggh, this is even more annoying than seeing someone 
using the name "Serena Tsukino" in a fanfic. :P

Regarding the sex scene between ->USAGI<- (:P) and Rei, I believe that 
Usagi overpowered Rei too easily. Rei is supposed to know some martial 
arts, significantly more than Usagi does. 

IMHO it gets too violent when Usagi starts slapping Rei and calling a 
bitch, and later on after Usagi unties Rei and Rei beats up Usagi. Many 
of us lemon readers prefer the lemons that are set up by love (and 
sometimes seduction), but not dominance and violence. I was hoping for a 
nice lemon scene where Usagi seduces (not dominates) Rei and makes 
passionate love to her.

Regarding your choice of pairing (i.e. Usagi/Rei), it seems a little 
weird. Usagi gets along the LEAST with Rei, and isn't Rei not supposed to 
have sex until she's married, being a shrine maiden and all? Minako and 
Usagi seem to be a better pairing, IMHO.