We are mere vessels. You have been given a greater purpose.
Like all Genomes, Mikoto is blonde, wearing her hair with pink clips, and has a tail. She has bright green eyes and a pale complexion. Mikoto wears a pink and white cropped top over a long-sleeved black one, a pink-and-white patterned skirt, and boots of the same color.
Quiet and formal, Mikoto, as the only Genome in Bran Bal with a soul, is intelligent and understands what her fellow companions cannot. She appears cold but is merely truthful, and while able to express her emotions, it can be assumed that she is used to not doing this as she lives alongside other, emotionless Genomes, and thus has difficulty showing how she feels.
Unlike the rest of them, Garland gave me a soul, that I may replace you and Kuja.
Garland created Mikoto less than a year ago, appearing as a 15 year old girl, sensing it was time for Zidane Tribal to return to Terra and wanted to create someone to guide him once he would arrive. She was also created as a substitute in the event that Kuja and Zidane were to fail their shared mission of unleashing chaos upon Gaia. After the party touches down on Terra, Mikoto leads them on a hide-and-seek chase to the Genome village of Bran Bal. Zidane meets her in the town's laboratory, where she explains their nature as Angels of Death.
Disgusted and confused by this, Zidane flees Bran Bal to find Garland and is imprisoned in Pandemonium. When Kuja's Ultima spell hits Terra, destroying the Genome city, Mikoto and the other Genomes board the Invincible and escape with Zidane and his crew.
When brought to Gaia, the remaining Genomes are taken to the Black Mage Village to live with the black mages, as Vivi mentions that since both races were created as vessels, they could understand each other. When Zidane and his party leave to defeat Kuja, he asks the black mages to take care of his "little sister".
While Mikoto was not seen on the deck of the Red Rose during the Second Battle of the Iifa Tree, considering the Hilda Garde III and Red Rose remain around the Iifa Tree to wait for the party, she appears on deck later after Necron falls, alerting Beatrix that the party has escaped Memoria. Because of her presence on the Red Rose at the time, it is possible she is the reason Lindblum and Alexandria learned of Zidane's plan to storm Memoria.
During the ending an unknown voice delivers a monologue. The speaker tells Kuja that although his actions were wrong, he gave "us" hope, as he was able to defy his fate. The group the speaker is referring to was "created for the wrong reasons", but Kuja's example has demonstrated that they too can live, and for this reason, they will ensure his memory lives on. The speaker is unnamed but appears to be Mikoto speaking for the Genomes as she is visible in the background during the monologue.