Irina is a very happy, upbeat person, as well as a devout Christian. During her first appearance in the series, she was very harsh towards those who she perceived as an opposition to her religion. This was demonstrated by how she and Xenovia treated Asia when they first met, as well as her reaction to Xenovia becoming a Devil. The God of the Bible was the center of her world, but with the discovery of His death, she has transferred her belief to Michael (the current “God”).
Irina first appears in Volume 3 in a picture with Issei from when the two were playing together. Her first appearance in person was alongside Xenovia under the orders of the Church to retrieve or destroy the stolen Excaliburs from Kokabiel and his men. She was defeated by Kokabiel while infiltrating his base and was left in a near death state by Kokabiel but was able to escape the worst with Asia’s help. At the end of the volume, Irina takes all the stolen Excalibur fragments back to the church, disappointed at the fact that Xenovia has become a Devil.
Like Xenovia, she is also a Holy Sword user (albeit through artificial means). She is a fast sword user just like Xenovia, and also a possessor of one of the seven Excaliburs, “Excalibur Mimic”, which has the ability to morph into different types of shapes that its user desires. However, her Excalibur was taken by the Fallen Angel leader Kokabiel during her introductory volume, and was later fused along with the three stolen Excaliburs into a single sword by Valper Galilei.
Later on as an Angel, she uses light-based weapons such as a light sword, a light bow, and arrows. In Volume 12, she used a prototype of the Holy Demonic Swords that Heaven had produced based on the sword Yuuto gave Michael during the events of the peace treaty in Volume 4. She later gained the ability to use different elemental attributes on the Holy Demonic Sword, ranging from fire, ice, and lightning.
She reappears in Volume 6 after being angelized as Michael’s Ace and moved into the Hyoudou Residence. When Issei entered his Juggernaut Drive, Irina was the one that brought the Oppai Dragon Song to the battlefield.
In Volume 9, Irina goes to Kyoto along with the second-year student of Kuoh Academy. She and the rest of the Occult Research Club then encounters Khaos Brigade’s Hero Faction where she fought against Jeanne but was defeated.
In Volume 11, she accompanies the Gremory Team to the Underworld, where they were attacked by Cao Cao and Georg, losing to the two. She was handed the Excalibur Ruler by Le Fay Pendragon to fix the broken Ex-Durandal after her brother abandoned the sword.
In Volume 12, Irina, Xenovia and Akeno faces Jeanne in a three-on-one match using a prototype Holy Demonic Sword created by the Heaven.
In Volume 14, Irina takes part in the rescue mission of the Occult Research Club’s kidnapped first-years and helps battle the Stray Magicians who took them.
In Volume 18, it is revealed that Micheal has crafted a special room that is located in a different dimension that would allow her to copulate with Issei without fear of falling. It is also revealed that she was Issei’s first kiss when they were children. In Volume 19, she started to become more bold in building her relationship with Issei, such as sneaking the doorknob that opens the special room in places he goes to, sneaking into his bed at night, bathing with him and calling him “darling.” She becomes slightly less concerned with falling in order to be with Issei, even offering to have sex with him.