In the "Melancholy of Haruhi Suzumiya" series, the narrator goes by the nickname Kyon.

The statement is true because throughout "The Melancholy of Haruhi Suzumiya" series, the protagonist and main character, who serves as the narrator, is referred to by the nickname "Kyon." This name is given to him by Haruhi Suzumiya herself in the first episode of the anime adaptation when she declares that she has trouble remembering names and assigns nicknames to her classmates. Kyon is the name that sticks with him, and it becomes a significant way of distinguishing him from the other characters. Additionally, Kyon is even referred to as such by the other members of the SOS Brigade, including Haruhi, Yuki Nagato, Mikuru Asahina, and Itsuki Koizumi. Therefore, it can be concluded that in "The Melancholy of Haruhi Suzumiya" series, the narrator goes by the nickname Kyon.