Hisana Kuchiki

Rukia's elder sister and Byakuya's wife. She abandoned her infant sister in Inuzuri to survive and spent the rest of her life searching for her.

She died of illness fifty years before the story, asking Byakuya to find Rukia and protect her without revealing that she had abandoned her. Byakuya keeps the promise, even at the cost of seeming the coldest of brothers.