Iris' Backstory

Repliforce scientists attempted to develop an ultimate fighting Reploid with both a high fighting spirit and peace-loving heart, but the differences were ultimately considered irreconcilable and the project was considered a failure. The scientists then decided to split them up into two Reploids, resulting in the creation of Iris and her brother Colonel. Her half was of the peaceful arbitrator, and Colonel's was of the strong-willed fighter.

The Erasure incident was Iris' first mission as a Navigator for the Maverick Hunters. She took the roles of both Navigator and item development by making power-ups out of the Maverick's DNA Souls. In the Xtreme Mode ending, Zero feels bad that her first mission was a tough one and the Colonel will blame him.

When the Repliforce was labeled Maverick after the Sky Lagoon incident, both X and Zero were assigned different missions to gather information about Repliforce's coup and to cut off their support lines. Iris assisted Zero on his missions as being his operator, like during the Erasure incident. However, Iris herself was part of Repliforce while her brother, Colonel, was Repliforce's second-in-command and therefore an imminent target for the Maverick Hunters. When the two of them battled in the Ceremony Hall of Repliforce's command center, it was Iris who stopped the two Reploids from terminating each other by begging her own brother to stop, since Zero had previously saved her life after the Sky Lagoon had crashed. Colonel, who had always regarded Zero as a friendly rival, backed off. Zero, on the other hand, stated that someone had to stop Repliforce at all costs, much to the grief of Iris.

When Repliforce's coup began, Zero rushed to the space port to stop the ascension of the military troops to the newly constructed space station of Repliforce, Final Weapon. There, he battled Colonel again, this time killing him. After that, Zero traveled to Final Weapon where he was encountered by Iris, who was blinded by the grief of losing of her brother and anger for Zero killing him. She had salvaged Colonel's control chip from his remains, fusing it with her own programming, thus causing her body to transform into a massive winged Ride Armor-like combat form which Zero was forced to battle. Even though Zero didn't mean to, he damaged the exterior power core of the structure, resulting in the destruction of the armor. In addition, Iris's incorporation of the salvaged control chip for Colonel also fried her programming to be irreparable. Zero hurried to Iris's body, but, it was too late to save her, and while she lay dying in his arms, she whispers to him that she did all this because, even though she knows it is nothing more but a fantasy, she wanted to live in a Reploid-only world together with Zero. Zero, totally overwhelmed by her death, began questioning his own reasons for fighting, becoming the infamous "What Am I Fighting For!?" scene.

Sigma would later antagonize Zero further, by revealing his involvement in the whole ordeal. He even taunts him by saying, "Iris is waiting for you!" before their battle.

After Final Weapon is destroyed, Zero flies back to Earth in an escape shuttle, but he is tortured by the thought of being unable to save anyone.