Kirika Kusanagi is one of the brightest, smartest and most popular students in Kyoto High School. So popular in fact, she attracts half of the school's male attendees. But despite all of this, she entrusts her friendship with her two fellow classmates, Akane Asamiya and Yoriko Yagami. One day the trio went on a field trip to the local genetics laboratory near Downtown Kyoto when a fight broke out nearby where the girls are touring between an industrial spy and an operative of British Intelligence MI6. The girls soon investigate the area, where the saboteur inadvertently crashed into a vast of Erlenmeyer flasks containing chemicals and mutated genetic bacteria. The mixed spillage created an after fume that filled the room where the girls are. The saboteur and the MI6 operative escaped, but the room suddenly sealed of and trapped the girls, forcing them to suffocate under the vile fumes, only two be saved a few seconds later by the area's ventilation system. After the incident, the girls physiology were slightly altered as the result of the fumes, giving them extra-sensory powers including a "mental warning" radar-like sense that warns them of danger. This led to a chain of events that forced Kirika and her friends to join MI6's Tokyo branch as part of a task force dealing with the activities of the notorious international crime organization SABRE. Kirika, who was partly responsible of her friends fate, becomes the brains and tactical field commander of the trio, who are given my the agency the codename of "Undercover Cuties"

      Kirika is the team's resident tactician, analyzing mission situations and tactics. She is also the coolheaded of the girls. Determined to solve a serious situation with brains instead of brute force. She is the moral compass of the trio, especially tried to resolve constant arguments between Akane and Yoriko. Despite her enormous beauty, Kirika depends more on strong will and intelligence over physical features. Her favorite hobbies include working with chemistry sets and reading romance manga (Japanese comics). Her favorite food is beef teriyaki.

      Like her friends Akane and Yoriko, Kirika possesses, as the result of the fateful lab accident, a sixth-sense "danger" radar, a psychic radar that warns hear of nearby danger or immanent physical harm. She also develop superhuman agility and reflexes from the accident. She is a well-trained athlete, gymnast, swimmer and diver. She is a black belt in karate and judo and well as close-quarters combat techniques. As a top agent in the MI6, she gains access to agency's prototype gadgets, weapons, vehicles and aircraft. Her standard mission weapon/gadget is a grappling hook pistol and carries a secretly concealed utility belt containing such items such as smoke bombs, non-lethal shurikens, a microfilm camera, a miniature MP3 recorder, and an optional sleep dart wrist gun. She is a qualified aircraft and helicopter pilot and has extensive training on advanced tactical driving. She has expertise in disguises and theatrics useful for undercover work. She also has extensive intelligence and survival training.