Tsukihi is the sister of Karen and Koyomi Araragi in the Monogatari franchise.
While still an embryo in her mother's womb, Tsukihi was replaced by an immortal phoenix and was born and raised as if she was a normal person. The only people aware of this are Koyomi and Shinobu, who learned of it during Tsukihi's teenage years but decided to keep it a secret from her and treat her as they always had.
Tsukihi is a character from the Monogatari franchise and has made appearances in the light novel series written by Nishio Ishin, featuring illustrations by Vofan, and published by Kodansha. She has also made appearances in the anime series based off of these light novels: Bakemonogatari and Nisemonogatari, both of which are produced by Shaft and published by Aniplex . Her original design is credited to the writer and illustrator of the light novel series while her anime appearance is credited to Akio Watanabe. She makes her first appearance in Bakemonogatari #2.