Kaname is the main female protagonist of the story, and appears at first glance to be a "normal" 16-year-old high school student. The character was taken from a friend of the authors, whose name was also Kaname Chidori, living in Japan. The discovery of her Whispered abilities attracts the attention of terrorist organizations. As a result, Sousuke has been assigned by Mithril to protect her. While Sousuke Sagara's battle intuition generally saves her from dangerous situations, she often considers Sousuke's instincts an irritant in daily high school events, leading to countless comical situations. Nonetheless, she and Sousuke continue to grow closer, to the point where they have expressed their feelings for each other.
Kaname's Whispered abilities also grant her an inherent knowledge (but not necessarily understanding) of advanced mathematics and science. It is no surprise then, that she consistently achieves top scores in these subjects at school. Her abilities as a Whispered, however, are a bit buggy. She does not know her full abilities, and also sometimes enters a near-trance, in which she understands Black Technology completely.
After a point in the series, she makes it obvious to herself that she likes Sousuke, but that does not stop her from hitting him with her harisen. Kaname is very easy to anger, especially considering Sousuke's antics. A humorous comment made by Kurz Weber about her anger was when he saw her lose her temper and commented, "What happened to my angel?" A majority of the stunts pulled by Sousuke will cause Kaname to go into a fit of rage and either hit Sousuke or chew him out. However she has a soft spot for him and when he does a good job she will often cook for him or give him a compliment.
Kaname is constantly battling with Teletha "Tessa" Testarossa for Sousuke, although the two usually end up either making fools of themselves or hurting him.
Kaname's bravery and determination came to a head in the climax of the novel Continuing on My Own. Following Sosuke's defeat by the hands of Leonard Testarossa, she gives herself up to Leonard and Amalgam to save his life. As she is picked up by the Belial's giant hand, she whispers something to Sousuke before being whisked off. After being taken by Leonard, she was imprisoned at an island villa by Amalgam. In the novel, Come Make My Day, Sousuke arrives at the island in order to save Chidori, but is unable to do so, because she's taken away in a helicopter. During the flight, Kaname is able to communicate with Sousuke, and that's when they both confess their feelings for each other, and Sousuke promises Kaname he'll find her no matter what the cost is.
She also developed feelings of guilt in the novel End of Day by Day (anime: The Second Raid) at having missed her opportunity to kiss Sousuke—after personally giving him a haircut—and thus having her first kiss "stolen" by Leonard Testarossa, as well as missing numerous opportunities afterwards to admit her feelings of love to Sousuke. At the end of the novel Come Make My Day she finally expresses those feelings to Sousuke while in radio contact with him and extracts an absolute promise from Sousuke that they will kiss the moment they are reunited.
In the most recent novel, Semaru Nick of Time, the origin of the Whispered is discovered to be from an accident during a Soviet experiment using an "Omni-Sphere" that occurred on December 24, 1984—when all the Whispered were born. Leonard Testarossa takes Kaname back to the Omni-Sphere after recovering from his wounds in Come Make My Day. There she is forced to resonate with Sophia, a key Whispered, who overtakes Kaname's personality. Under Sophia's control, Kaname is shown the illusion of shooting and killing Tessa Testarossa and Sousuke Sagara. Under Sophia's control, she leaves with Leonard for Merida Island, where Amalgam has built a machine to utilize a final ability of the Whispered; still believing she killed her good friend and the man she loves.
In the light novels, it is mentioned that her younger sister and father live in New York. Her mother died of cancer roughly 4 years before the start of the series. Shortly after that, Kaname ran away from home, but was returned home the next day. Kaname's relationship with Shizu, her late mother and Ayame, her younger sister, is apparently friendly, but she is more tense towards her father Shunya, who works for the United Nations as its environmental High Commissioner. Her late mother's family also seems to have strained relations with the Chidori family, at least until her grandfather from that side makes amends. Because of her sensitive past, she developed a "tough-lady" attitude, which has helped her deal with her past and survive several life-threatening situations. It is also revealed in the novel A Dancing Very Merry Christmas and on the Full Metal Panic! Anime Mission fan book that she shares her birthday with Tessa on December 24, 1984 on Christmas Eve.
Kaname lives alone in her own apartment, across from the complex which Sousuke lives in. While it is unknown how she earns money to support herself, it can be presumed that her father sends her money from New York. She also takes on multiple part-time jobs, sometimes inviting friends to join her. In the manga, this usually ends in catastrophe because of a certain sergeant. This is mentioned one time in the anime, while scolding Sousuke, saying she won't have enough money if she doesn't get any work. She began attending Jindai High School at age 15, and is currently in her second year. As mentioned before, she leads a normal lifestyle; she is the class representative, vice president, and is quite popular at school. However, after Sosuke Sagara transfers into her class, she was involved in several kidnapping incidents and battles against terrorists. Through Sousuke, Kaname meets various members of Mithril, and when not at school she became involved in many "adventures" of a sort, usually centering around herself.