Introduction
The Bleach universe centers around teenager Kurosaki Ichigo and his interactions with a host of spiritual beings having to do with the afterlife. The shinigami, who serve grim reaper-like functions, are one such entity he encounters, and thus change his life when he receives powers from a weakened Kuchiki Rukia. Generally, the reapers reside in Soul Society, the plane of existence souls move to after death. They are organized into the Gotei 13, or the 13 Imperial Guard Divisions, and are granted ranks in accordance with achievements and strength, and perform all sorts of functions such as defense and even scientific research.
Of course, the plot isn't all fun and adventure. Conspiracies, saving the material world, and discovering new powers and abilities are all in a chapter's work for this popular, long-running Shounen Jump series. Kubo Tite has been writing and illustrating it since 2001 and has exceeded the 500 chapter mark.
Kuchiki Byakuya is the first real antagonist Ichigo must face. He is the captain, or highest ranking officer, of the 6th Division and head of the Kuchiki family, one of the four oldest noble houses in the dimension. His first appearance in the story is to collect his adopted sister Rukia for sentencing in consequence of her violation of shinigami law.
Some Notes
If it hasn't become apparent yet, please note that I will be using the Japanese terminology for most well-known items, because that's just how I've familiarized myself with the series. I've tried to clarify the more obscure ones using descriptive tags, but if you find yourself confused, do let me know.