I had doodled this some time before finding out about Captain Kuchiki's "NDR" but it pushed me to color and share.
A spoiler-infested explanation can be found in chapter 469.
I'm often surprised at the lack of this pairing on the internet; I've always loved their cat/mouse foreplay.
Well here's my first try at both captain and former captain, so I wanted to show off both Yoruichi's shunpo and Byakuya's senbonzakura.
For higher res, download it from deviantart