Kyoko Kirigiri, heir to a family detective legacy, underwent rigorous childhood training under her grandfather, Fuhito Kirigiri. This training enforced strict traditions valuing detective work above personal relationships. She achieved official detective status at age 13 with DSC number 919, participating in cases like the "Sirius Astronomical Observatory Murder Case" alongside Yui Samidare. Seeking to reconnect with her estranged father, Hope's Peak Academy headmaster Jin Kirigiri, she enrolled as the Ultimate Detective. During the Killing School Life, Kyoko initially hid her detective talent due to memory suppression, appearing as the "Ultimate ???". She maintained a stoic, analytical demeanor, methodically investigating murders while suppressing emotions to remain objective and project calm. Despite this guarded nature, she formed a strategic alliance with Makoto Naegi, gradually building mutual trust. Discussions about her father triggered intense reactions, and visible distress surfaced when Alter Ego suggested Jin might be the mastermind. Significant trauma included burns on her hands from a childhood attempt to save a friend, leading her to constantly wear concealing gloves. She only revealed these scars to those considered family, eventually showing them to Makoto. After the Killing School Life, Kyoko joined the Future Foundation as director of the 14th Branch, combating remnants of despair. She became more considerate and expressive within trusted circles, engaging in gestures like hugging or hand-holding (sometimes without gloves). While remaining reserved with outsiders, she demonstrated loyalty to allies, particularly Makoto, actively supporting him during leadership conflicts within the Foundation. In the Future Foundation killing game, Kyoko wore a poison-injecting bangle programmed with a personalized "NG Code": Makoto surviving beyond the fourth time limit. Discovering this code, she deliberately withheld it from him to prevent his reckless self-sacrifice. She succumbed to the poison after the fourth time limit expired. However, the Hope Arc revealed her survival through medical intervention by Mikan Tsumiki, facilitated by the late Koichi Kizakura's final request. Concluding scenes showed her alive at the rebuilt Hope's Peak Academy, acknowledging Makoto in his new role as headmaster.