Kyrie wears a white dress with black boots, similar to what other citizens of Fortuna are seen in. For most of the game, she also wears a necklace given to her from Nero. It appears to be a golden miniature of a four-winged angel with a red crystal in the center.
Kyrie was born and raised in the city of Fortuna. She is the younger sister of Credo (the leader of the Order of the Sword's Holy Knights), and songstress for the Festival of the Sword. Kyrie is also the childhood friend and love interest of Nero. The three of them grew up as a family. Kyrie and Credo's parents were killed by demons. At some point, a number of demons appeared suddenly from the Mitis Forest (the forest that surrounds Fortuna) and attacked the city. During this incident, Kyrie was injured but would recover completely.
At the beginning of the game she is seen singing Out of Darkness at an Order of the Sword gathering, occasionally glancing at the empty pew where Nero is supposed to be. Nero appears just before the song ends, and he hands her a small gift as she comes to sit beside him while Sanctus explains the history of Sparda's rebellion against Mundus and his demon brethren.
As the people begin to pray, Dante crashes in and shoots Sanctus, causing widespread panic which briefly separates Nero from Kyrie. She drops the gift given to her in the confusion, and it is quickly trampled. As Dante approaches her brother Credo, Kyrie is knocked down and cowers in fear before Nero comes to her rescue. Credo orders Nero to hold off the assassin while he takes Kyrie to safety and fetches help. After Nero's skirmish with the Devil Hunter, Kyrie brings him his custom sword. While he prepares it for battle, she locates the contents of her package--a necklace--and puts it on. Afterwards, she goes with Credo as Nero investigates the demon uprising that Dante reportedly caused.
Kyrie later arrives to witness Nero with his demonic arm standing over a defeated Credo. Unaware that Nero defended himself against Credo who was infused with demonic power, Kyrie steps back in shock as Nero tries to explain what happened. Suddenly Agnus arrives and uses the confusion to kidnap Kyrie and flee.
Later, under the command of Sanctus, Kyrie is kidnapped by a Bianco Angelo, taken to the Savior and absorbed into its forehead. Nero comes to her rescue and promptly defeats Sanctus Diabolica. The madman threatens to kill her if he advances further, but Nero tosses the Yamato to the false prophet to distract him, then slams him into a wall with the Devil Bringer. With a swift cut from the Yamato, Nero frees Kyrie and impales Sanctus, killing him. Nero escapes the confines of the Savior with Kyrie safe and sound. Sanctus returns as the False Savior, but Nero quickly attends to the matter by pulverizing the twisted visage of the statue while Dante and Kyrie watch.
After settling matters with Dante, Nero approaches Kyrie cautiously, unsure of how she will react to his demonic powers. She responds by taking his Devil Bringer in her hands and expresses her desire to be with him, regardless of his nature. The two almost exchange a kiss, but some Scarecrows show up to interrupt the moment. Kyrie patiently waits for Nero as he attends to the matter, afterwards they are finally able to share their long-awaited kiss.
Kyrie was told by Nero to stay inside due to the cloaked figure who takes Nero's demon arm.
Kyrie made a cameo appearance in Onimusha Soul.
- Her name is taken from Kyrie eleison ("Lord have mercy" in Greek), the first part of the Catholic Ordinary of the Mass. It was traditionally sung in Greek and was translated later in Latin.
- The character is voiced and motion captured by Laura Napoli in Devil May Cry 4.
- Kyrie is the only non-playable human character in Devil May Cry 4 who can be seen during gameplay. In Mission 9, she can be seen in the cage in which she appears after the fight with Agnus.