Aside from his somewhat errant youth, Byakuya drinks very little. Always in moderation, and often only to be polite, he is very careful not to become tipsy both to preserve his strictly-maintained reputation and to prevent any mishaps. On very rare occasions–and only in the presence of people he is truly comfortable around–will he allow himself to relax those standards.
Being the only heir of one of the highest-ranking families in Soul Society, Byakuya spent most of his childhood isolated from those his own age ad made very few friends. One exception to this was a very persistent silver-haired prodigy who noticed his tendency to spend his time alone between classes at academy. A young Gin often pestered the standoffish noble into spending time together and, although Gin graduated in a single year while Byakuya took four, they remained friends and became rivals of sorts in the Gotei.
Despite what most think, the Kuchiki is not prudish when it comes to intimacy. Having grown up with beliefs akin to medieval Japan’s, sex is not a social taboo to him; although, since his involvement with Hisana and her subsequent death, he has little to no interest in casual affairs.
Bedroom/house/living quarters headcanon
Byakuya’s quarters are very typical of his rank: as the head of his family, he has an entire wing of the main Kuchiki manor to himself, including a study, private bathroom, lounge, and large bedroom. It is all very simply, but elegantly furnished with traditional furniture, but there are few aesthetic decorations. The two major rooms have shouji that open directly onto the veranda bordering his own personal garden.
Born from this image, I have an extensive Edo-era Japan/Yōkai headcanon involving the Bleach universe. Byakuya is one of thirteen Yōkai lords, a powerful Yōsei that may grant wishes in exchange for favors, items, and other things that interest him. He commands numerous other Yōkai of lower rank in his domain as well as the many Yōsei under his rule.
