Oasis - Champagne Supernova

There was a secondary reason Byakuya chose Renji to be his fukutaichou.

The primary reason was, of course, that he saw promise in the ex-streetrat, promise and potential for great things. But the secondary was much more subtle, and if the public knew, they would get a far clearer glimpse into Byakuya's character than the Kuchiki heir could ever allow.

Byakuya saw in Renji the need to overtake, to win, and to reclaim what Byakuya had stolen. He saw it and understood it, for that same need was heavy in his own bones, and always had been. He understood, too, that he had taken Rukia from his fukutaichou, suddenly and completely, and the injustice of that sat oddly with him, though it had been entirely within his rights. He was a Kuchiki, after all.

But injustice was not his way. Nor was letting slack the tension of competition with a great rival. That was all that drove Renji Abarai. And thus, though Renji was in no way great rival to him, Byakuya understood.

In giving Renji the position of fukutaichou, Byakuya was acknowledging the part of himself that he saw in the fiery redhead, no matter how opposite they seemed, no matter how they could never understand each other's behaviour. Their goals were ultimately the same.

In giving Renji the position of fukutaichou, Byakuya was giving Renji the chance, just the chance, to achieve those goals. Who knew - if he worked hard enough, he might even accomplish them.