Kaien Shiba was the lieutenant of the 13th Division, under Juushiro Ukitake, up until his death at the hands of a Hollow that also killed his wife, Miyako Shiba. Kaien, a very ethical man, was adored by many of the 13th Division members. He was outspoken and bore a rough disposition, but his down-to-earth attitude was one of the reasons why everyone looked up to him. Kaien treated his fellow company members indiscriminately, regardless of their social standing or rank. Because of this, he was popular among aristocrats and commoners alike within his Division. He was the first person in Seireitei to treat Rukia like an ordinary person since her adoption into the Kuchiki family. Until he came along, she was treated with careful respect to her face and talked about and bashed behind her back. She was grateful for the fact that Kaien treated her as an equal, and it has been hinted that Rukia may have come to develop romantic feelings for him because of this. She didn’t pursue him because Kaien was already married to the third seat of the 13th Division, Miyako Shiba. Kaien believed that one's "heart" was determined based on the prospects of fighting and protecting. He was a firm believer in Captain Ukitake's policy on fighting, which consists of two types of combat: 1) The fight to protect life, and 2) The fight to protect honor. Kaien took it a step further and believed they both end up being the same thing: "Heart." He believed that every time one connected with another, a little bit of "heart" is born between them. He thought of "heart" as not something inside you, but rather what is born whenever you think of, or remember, someone else. He believed that one's "heart" exists in others, and that it remains with his or her comrades even after death. Having held such views, he believed that people should never die alone. Kaien's favorite food was ohagi, and he liked to take afternoon naps if he could.
