(長門 有希, Nagato Yuki
?) is a fictional character in the Haruhi Suzumiya
franchise. She is initially portrayed as an introverted, taciturn bibliophile. She is actually an artificial human created by the Data Integration Thought Entity, and possesses supernatural powers as a result. She never officially joins Haruhi Suzumiya's SOS Brigade, but observes and takes part in club activities on the behalf of the Entity while still being the only member of the Literary Club. In addition, she is present to ensure that Haruhi does not use her godlike powers, and aids the other Brigade members in stopping forces that cause her to do so. The alternate Yuki established in the fourth light novel, The Disappearance of Haruhi Suzumiya
, is the main character of the spin-off manga The Vanishing of Nagato Yuki chan
Apparently, Yuki has extremely pale skin, as there are numerous times in the original light novels where Kyon describes her face, neck, hands, or fingers (as she flips the pages of the book she is reading) as "white". Also, Kyon always comments on Yuki's uncanny ability to walk "soundlessly" (this can be seen in the anime when Yuki is exploring a public library with Kyon who appears puzzled by it). Yuki is attractive enough to earn an "A-" grade from Taniguchi and, as Taniguchi states, has a lot of secret admirers. In The Disappearance of Haruhi Suzumiya
, when Kyon came face to face with Yuki in a twilight realm (here she is simply a normal, shy girl) blushing in front of him, he was stunned by her and even felt for a moment that it would be good to stay in this realm and join the Literature Club for good. She initially wears glasses, but forgets to regenerate them after they are broken whilst she is protecting Kyon from Ryoko. When she realizes she no longer has them, Kyon tells her she looks cuter without them, prompting her to leave them unregenerated.
Yuki Nagato is a quiet high school freshman that is the only member of Haruhi's SOS Brigade that willingly joined and was not "voluntarily arrested," or forced into joining, by Haruhi Suzumiya. She was a member of the Literary Club, whose other members were all seniors who graduated, leaving Yuki the sole member of the club. She lives alone in the same apartment complex as Ryoko Asakura, in room 708. She wears her school uniform almost all the time (even on non-school days). She initially wears glasses but, after the confrontation with Ryoko Asakura, they broke. She planned to create new ones, but decided against it after Kyon told her that she looked cuter without them. She wears a different outfit for the first time when the SOS Brigade goes on vacation to the remote island in "Remote Island Syndrome".
Yuki is a "humanoid interface", or artificial human, created by the Data Integration Thought Entity, a god-like alien figure, for the purposes of interacting with and observing events on Earth. She was created 3 years ago and, though possessing the exterior of a high schooler, she is in fact about 1,319 years old, when one takes into account the time she has spent outside of Haruhi's universe. Specifically, she has been created to observe Haruhi, who can create huge quantities of data from nothing. Haruhi represents a potential route to autonomous evolution, an ability that the Overmind does not have and one which could help accelerate the evolutionary standstill the Overmind has reached.
As an artificial human, she has numerous paranormal abilities. She is capable of manipulating the properties of the environment and any materials within it at any scale to her desire, referred to as "bogus magic" by Kyon. For instance, she can modify the "elemental boost information" of a baseball bat to hit only home runs, nullify data links (removing other artificial interface connections from their bodies), plus she is able to make a cover-up story (since Ryoko was gone, she made a cover up story that she moved to Canada), and reconstruct a classroom, down to the last detail, after everything in it was completely destroyed. As a result, she is capable of feats of superhuman strength, agility, and stamina. In one instance, she was unfazed while impaled by multiple metal spikes, and effortlessly reconstructed her body afterwards. Her state also affords her an extreme level of intelligence. She can comprehend the rules and concepts of a game instantaneously, as well as create flawless strategies based on her observations, and was able to learn how to play a guitar mere moments after picking one up. However, she has been seen to be fallible, such as when she reconstructed the devastated classroom but forgot to reconstruct her broken glasses. Yuki also has a lack of understanding towards social norms and earth technology, as demonstrated by her bluntly literal future predictions and her clumsy attempts at using a computer mouse. However, it can be construed that the mouse incident came from her watching Kyon hold the mouse away from Mikuru. This is likely due to her self-imposed state of near-total isolation in order to interfere with as little of the environment around Haruhi as possible.