The story revolves around Haruhi Suzumiya, a high school girl obsessed with finding all forms of the extraordinary and supernatural, and Kyon, a cynical classmate who proclaims his non-belief in such matters and narrates the series. After being displeased with the mundane happenings at school and the lack of interesting after-school clubs, she forms her own, the SOS Brigade, to investigate any mysterious happenings, with Kyon forcibly drafted as its second member.
As the series progress, Haruhi recruits three additional members into her club: the silent bibliophile Yuki Nagato, the shy and timid Mikuru Asahina, and the friendly "mysterious exchange student" Itsuki Koizumi. These members are, in time, revealed to be the extraordinary characters she is seeking (Yuki, an artificial human created by the extraterrestrial Integrated Data Entity; Mikuru, a time traveler; and Itsuki, an esper), sent by their various organizations to observe Haruhi. All see Haruhi as possessing a superhuman control over the universe, capable even of recreating the entire universe in a state of dissatisfaction and attempt to prevent this by keeping her entertained, holding her powers in check, and maintaining the illusion of a normal life.