Yuki Nagato is a member of Haruhi Suzumiya's SOS Brigade from The Melancholy of Haruhi Suzumiya. She initially appears as a shy, silent girl who loves books. In reality, Nagato is a Humanoid Interface, sent by the Data Integration Thought Entity to observe Haruhi's unpredictable powers. She also manifests various powers and abilities; however, these can only be used minus Haruhi's presence and observation.
Nagato's personality varies from time to time. In "The Disappearance," Nagato is given more emotions, is desperate for Kyon's affection, and is easily frightened. And in the spin-off, "The Melancholy of Haruhi-Chan Suzumiya", her character is enhanced as an otaku gamer who plays erotic video games and spends the time in her apartment subjecting a miniature Ryoko Asakura and Kimidori baloon dog to her strange whims.
- Reading books
- Computers and programming
- Playing eroges
- Playing her electric guitar
- Hacking into the Computer Research Society's game play
- Kyon, although her emotions are often repressed
- Toying with Achakura and Kimidori
- "There might be discrepancies in the transmission of data."
- "I am not referring to the absence of universally accepted personality traits; what I mean is literal, that Haruhi and I are not like other organic lifeforms such as yourself."
- "I forgot to recreate the glasses."
- "You and Haruhi Suzumiya disappeared from this world for two hours and thirty minutes."
- "It is possible, but I would advise against it."
- "Any alteration of the regional climate could possibly have devastating aftereffects on the ecosystem of the planet."
- "You know you want it. You know you want it. You know you want it."
- Both Nagato's Japanese and English voice actresses also voice Minami Iwasaki from Lucky Star, who is similar in personality.
- Kyon and Nagato themselves make guest appearances in one too many Lucky Star episodes.