Higashidani Uki is the middle child of the Higashidani family and the younger sister of Higashidani Sanosuke. At the age of sixteen, Uki is the cornerstone of her small family in rural Shinshū, acting as a disciplinarian for her father Kamishimoemon and protector of her younger brother Ōta. Apart from her serious and short-tempered side, however, is a young girl with her head in the clouds and a pronounced confidence in her own looks; she frequently misunderstands situations, believing that any conflict that arises around her is some duel for her hand and that young men who insult or ignore her are merely doing so to hide their passionate adoration of her beauty.
In her youth, Uki was known as a cute little girl who would follow her older brother around wherever he went, but when Sanosuke left home to join the ill-fated Sekihō Army never to return, and her mother fell ill and passes away, Uki became incredibly depressed and afraid of losing more family members. As such, she has become rather uptight about Ōta's safety and orders him to hide immediately when trouble arises.
After Sano left again to team up with Kenshin Gumi to bring Kaoru back (who was at the time held hostage by Yukishiro Enishi), Uki suspects that that man may be her long-lost brother.
- Like the rest of the Higashidani family, the origin of her name comes from a direction, in her case the kanji U means "Right".