Iris

Iris (アイリス) was Zero's Navigator in Mega Man X4 and Mega Man Xtreme 2. She was also the younger sister of Colonel.

Mega Man Xtreme 2
The Erasure incident in Mega Man Xtreme 2 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 DNA Souls. In the Xtreme Mode ending, Zero feels bad that her first mission was a tough one and the Colonel will blame him. This is the first chronological indication of Zero's feelings for Iris.

Mega Man X4
When the Repliforce was labelled 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 down. 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.

thumb|250px|right|Zero loses himself in pain after Iris' death, shouting the now famous (or infamous) line, "WHAT AM I FIGHTING FOR?!"

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 her grief of the loss of her brother and anger for Zero killing him. She had salvaged Colonel's Control Chip from his remains, fusing it with her own programing, thus resulting 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. He hurried to Iris' body. However, it was too late to save her. Whispering to Zero that she did all this because she wanted to live in a world for Reploids only together with him, she died in his arms and Zero, who was totally overwhelmed by the pain, began questioning his own reasons for fighting.