Kyoko was an amnesiac and was titled as Ultimate ??? at first. Later, it was revealed that her true identity is the Ultimate Detective. She is also the daughter of Jin Kirigiri, the deceased Headmaster of Hope's Peak Academy.
In Chapter 5, the mastermind attempts to have her executed for the murder of Mukuro Ikusaba, a crime she didn't commit, due to her interference in the masterminds plans. However Makoto Naegi sees through this, but is almost executed himself, which was stopped due to the interference of Alter Ego. However she is executed in the bad ending.
Kyoko survives the final trial and escapes Hope's Peak Academy with the other survivors. Kyoko also appears in Danganronpa 2: Goodbye Despair as a member of the Future Foundation. She's also seen in Danganronpa/Zero.
A light novel series based on Kyoko's past with Yui Samidare has been published, titled Danganronpa Kirigiri. [Source: wikia]
You can download this papercraft toy here: Danganronpa - Chibi Kyoko Kirigiri Free Paper Toy Download [Instruction]