Squee! Loved reading this - Byakuya's calm detachment (even while he makes mistake after mistake) and Renji's drunken cheerfulness made for such a wonderful combination. The way you got both their voices down was very wow-inspiring, too, although my favorite line would have to be:

A grammatically complex response might short-circuit what few working brain cells he [Renji] had left.

*very wide grin*