Kiyone Kotetsu is the co-3rd seated officer/acting lieutenant of the Thirteenth Division in the Gotei 13 under Captain Jūshirō Ukitake, sharing her position with Sentarō Kotsubaki.

Kiyone is the younger sister of Isane Kotetsu, the Lieutenant of the Fourth Division (the medical and supply relief division). Unlike her sister, Kiyone is very open and excitable but she does share Isane’s sense of loyalty.

She holds her captain, Jūshirō Ukitake in high regard and always tries to impress him in any way possible, even if she has to ruin her partner Sentarō Kotsubaki to do so. Like other female Shinigami she is a member of the Shinigami Women’s Association.
Kiyone’s infatuation with her Captain is often a source of comic relief, as she frequently engages in competition with Sentaro over who admires and/or loves him more, much to Ukitake’s exasperation. In one omake chapter, she is even willing to help Soifon pin Ukitake to a tree with kunai knives and slash open his clothing so she can have “sexy” photos of him, although she does jabber “I’m sorry, I’m sorry!” while she photographs him.

(Source: Bleach Wikia)