Character:

Byakuya Kuchiki is the 28th head of the noble Kuchiki clan, one of the four great noble families in Soul Society. As such, Byakuya acts in an aristocratic manner — he seems always serene and apathetic towards other people, even when he is actually deeply conflicted. He is also extremely calm, even in battle, and is very seldom surprised by even the most drastic of actions. Ironically, when he was younger, he was quick to anger and very hotheaded, as noted by his grandfather, Ginrei Kuchiki; similar to the way Ichigo and Renji are now.

Source from Wikipeida