User blog comment:Xilinoc/Everything but the Rain op. 8 - "The Defenders"/@comment-4620155-20130502112415

Anyone else remember Byakuya's hatred of the Shiba Clan? (He released his Shikai on a Soul simply because he was from this clan).

We don't actually know why he hates the clan so much, so perhaps it has something to do with Isshin? (Unless it's got something to do with Kaien instead.)