While he is aware that Kaien's memories and being are in this arrancar, he still cannot reconcile that Kaien is still around. His shadow afflicting everything. It was like a bad nightmare ---- a dream that was inescapable. Or, perhaps this was Byakuya's obsession ---- his distaste for the man creating demons where there are none. Despite the fact that the other would have no reals power if Byakuya ceased reacting, he finds himself reacting anyway because his ire morphed into a reactive white hot blade that consumed his very being.
Just hearing the man's words made Byakuya stiffen. It truly was insideous the way Kaien's memory would grasp a hold of him and claw at his very being. That smile. That smile drives him up the wall, becomes a darkness that obscures everything. All Byakuya can think is that this man is absolutely fucking with him. The irony of it all is that Byakuya spoke first. Had he ignored this man's presence and ignored him now then this interaction would cease and eventually the espada would grow bored.
But no. He cannot do that. Far be it from him to ever do such a thing. He never could as a spoiled brat of a teenager and now as an adult and head of the Kuchiki clan, he cannot do that. He just cannot let this ire, this tirade simmer and instead fans the flames of his rage, bearing the full might of his glare at the espada before him.
❝ Fuck you. ❞ In eloquent, but he doesn't care anymore. He's pissed. He's so pissed his entire frame trembles.