Out of all the club members of the S.O.S Brigade, Kyon can be considered to be the only normal member of the group. Despite not having any powers or special abilities, Kyon is the most important member of the Brigade. In a different sense, Kyon serves as a foil for all of the characters in the series, he counteracts Haruhi Suzumiya's brash and impulsive nature with his calm, and self composed. He counters Itsuki Koizumi's flamboyant flare with a more down to earth view of the world. He contrasts Mikuru Asahina's shy personality and Yuki Nagato's quiet one with a more vocal and self confident approach to situations. As a member of the S.O.S Brigade, it's Kyon that serves as the humanizing element, and he's the only person within the entier group who has a complete understanding of each members personal situation, and when any of the members has a personal problem, it's Kyon they go to for help, not Haruhi or anyone else, it's always Kyon. Most important of all, Haruhi often ignores requests from other people, but it's usually Kyon's statements that defer her and make her usually stop an act, as seen during the Baseball game, where it was Kyon that suggest they take the win, but withdraw from the tournament, to which Haruhi complied to.
As a person, Kyon, as described by Sasaki in the Dissociation of Suzumiya Haruhi, Kyon has "... the qualities of a listener, with the right amount of intelligence, as well as that of innocence," and that Kyon gives "a feeling of being able to talk" to him freely. In this sense, this would explain why when any serious event occurs, from Mikuru's kidnapping to one of Haruhi's closed spaces threatening to destroy the world, it's always Kyon whom the task falls upon to resolve this.
The weirdest thing about Kyon is that, even though everyone in the series refer to him as Kyon, that is actually not his real name, it's a pet name created by his little sister, but from descriptions by Sasaki, Kyon's real name is "royal and imposing", further elaborating on the mystery of Kyon's real name.
The Melancholy of Suzumiya Haruhi:
In the Melancholy of Suzumiya Haruhi, Kyon sat right in front of Haruhi, and was the closest person to her when she made her famous introduction, "My name is Suzumiya Haruhi. I graduated from East Junior High. Normal humans don't interest me. If anyone here is an alien, a time traveler, slider, or an esper, then come find me! That is all." Despite all the efforts of everyone else in class 1-5 to get Haruhi to talk, it was infact an offhanded remark that spurred Haruhi to actually hold the first conversation she had with anyone in the entire school, and it was another off handed remark of his that spurred her to create the S.O.S Dan. As Haruhi went around recruiting club members, well stealing snatching people from other clubs and classes against their will as so they can join her club, Kyon sat in the clubroom stolen from Yuki, president of the Literature club.
It wasn't until all the members of S.O.S Brigade was gathered where things began to get weird for the normal human, Kyon. After being called out to Yuki's house in the dead of night, she reveals to him that she is an alien. After that, it's Mikuru who reveals that she's a time traveler, and Itsuki tells him that he is an esper. Through a series of events, Itsuki shows Kyon the closed spaces that are created by the instabilities in Haruhi's mind, and that it's actually Kyon's fault these spaces are continually popping up. Before meeting Kyon, Haruhi was more stable, it wasn't until after meeting Haruhi where the closed spaces began to show up more frequently.
Despite all this, Kyon was able to continue on with life until one day in the club room where Haruhi saw Kyon and Mikuru fighting over the computer mouse, and she got jealous. That very night, Haruhi and Kyon were trapped in a closed space, after communicating with Yuki via the club room computer, it was revealed that Haruhi was creating the world anew, and that the only person who could save the old world was Kyon. In order to remind Haruhi what made the whole world so special, he kisses her, and the next morning all was well.
This novel of the series ends with Kyon arriving to the S.O.S Brigade's usual meetng spot next to the station before Haruhi, for the first and most likely the last time.