Yukito is a wanderer travelling across the country in order to find the 'girl in the sky', a goal each generation of his family has passed on for a thousand years. Yukito lives off his trade, a special form of stringless puppeteering that was taught to him by his mother before she died. He is a successor and descendant of Ryūya and Uraha.
During his time in Kami Yukito meets several young girls and the strange events that befall them, including his temporarily becoming a member of Minagi Tono's astronomy club and doing odd jobs for Kano's older sister Hijiri. He forms a deep relationship with Misuzu Kamio in the time they spend together, but after Misuzu falls ill during his stay he decides to leave after learning that her "illness" grows worse whenever she begins to become friends with someone. After having a change of heart and recognizing his concern for the girl, he begs for another chance to watch over her.
Movie version
Yukito from the Air Movie
In the Air Movie, along with a re-worked version of the story focusing on the relationship between Yukito and Misuzu, Yukito's personality takes on a more cynical edge as well as a slightly older appearance. He came to Kami in order to perform at the upcoming festival, and at one point claims that he doesn't want to perform for families only pretending to be happy, implying that his own family life may have been difficult.
He is initially annoyed at Misuzu's attempts to be around him, glaring at her bringing him juice because of the heat. After helping Misuzu with her summer project (for which his reward was to have her buy him a bowl of ramen since he hadn't eaten well in days), he gradually warms up to the girl and her eccentric aunt Haruko after being invited to stay at the Kamio residence.
In this version of the story, Yukito is more obviously stated to be the reincarnation of Ryūya. Thus, Yukito recalls his past life, and the guilt he feels for what happened to Kanna, who was his lover in the movie. His relationship with Misuzu is much more overtly romantic, and he confesses his love for her near the end of the film.
Trivia
During episode 9 of The Melancholy of Haruhi Suzumiya Yukito's line "Ramen set!" from the first TV episode can be heard in the background during one scene. This may be an in-joke since Daisuke Ono, the voice of Yukito, was also cast in that anime as leading character Itsuki Koizumi.
