Yuki Nagato

Yuki Nagato is a quiet high school freshman that is the only member of the SOS Brigade that was not "voluntarily arrested," or coerced into joining, by Haruhi Suzumiya. She lives alone in the same apartment complex as Ryouko Asakura. Yuki has a very stoic and introverted personality, preferring simple body language rather than speaking. When prompted to speak, she does so in a very concise manner, always speaking in a monotone and displaying a dispassionate complexion.

‎‎As it turns out, Yuki is a "humanoid interface," or artificial human, created by the "Integrated Data Entity" three years prior for the purposes of interacting with and observing events on Earth. Specifically, she is assigned to observe Haruhi Suzumiya, who was supposedly the cause of an explosion of data that occurred and significantly altered the world.