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 he meets and befriends the other forcibly recruited members he discovers they are exactly the kind of beings Haruhi sought to uncover and also dicovers unbelievable things about Haruhi.
Haruhi Suzumiya (涼宮 ハルヒ)
The title character and leader of the SOS Brigade, whose energetic and eccentric character proves to be a driving force for the series.
Kyon (キョン)
A student who unintentionally forms a relationship with Haruhi, and is the only normal human in the SOS Brigade. Even though Haruhi is the title character, the story is told through his viewpoint. Through narration and dialogue, he provides his insight, perspective, and opinions on the series' events.
Yuki Nagato (長門 有希)
A humanoid interface created by the Data Integration Thought Entity, whose responsibilities involve monitoring Haruhi and the investigation of an unexplained "explosion of data" three years prior to the present story. She possesses an ability to manipulate her surrounding environment.
Mikuru Asahina (朝比奈 みくる)
A time traveler from the distant future who is assigned to investigate the reason behind the inability to travel to any point time before three years prior to the present story.
Itsuki Koizumi (古泉 一樹)
An esper who, like members of "The Agency", suddenly acquired the power to explore Closed Spaces and combat Celestials three years prior to the present story.
Translation: Chris Pai (The Melancholy of Haruhi-chan Suzumiya)
Translation: Chris Pai (Nyoron Churuya-san)