Originally thought to be born around the late 20th century on Earth, Kira's origins are still not quite understood. Raised on Earth in the late 20th century, Kira's life was uncomplicated. He aspired to become a doctor at a young age, and was well on his way toward his career goals until a dramatic physiologic change began that caused Kira to question his humanity. Kira found that he was able to act as a conduit for multiple types of energy. With practice he discovered that he had the ability to control these phenomena to a limited degree.
One fateful day he decided to embark on an experiment to test the limits of his abilities, the result of which caused a violent spatial/temporal anomaly to form, which transported him to 24th Century Bajor. Completely in shock over what had happened, and in a state of medical emergency, Kira was found by a family of Bajorans who took him to the nearest medical facility. During the course of his recovery, Kira vowed not to try to utilize his capacities again and decided to remain on Bajor. Kira was adopted by the family that rescued him, becoming as a son to them and taking on a Bajoran name.
After completing his medical degree with dual emphases in exobiology and neurophysiology, Kira was assigned to the USS Ilion. His service to the Ilion was very brief due to an encounter with a tesseract that catapulted the Ilion into uncharted space. Although the details of how the Ilion was returned to Federation space is still deemed classified by Starfleet Command, it is known that it was during this time Kira's abilities were discovered. He was held for questioning by the Judiciary Board regarding his involvement after the destruction of the Ilion, but was later released and promoted to Lieutenant Junior Grade after the board heard of his "involvement" in the return of the Ilion.
Following the destruction of the Ilion Kira was given a year of "leave," where his abilities were tested and developed by a joint effort from the Medical and Theoretical Physics sections of Starfleet Command. Following this he was reassigned, along with some Ilion ex-comrades, to the USS Knight with a promotion to CMO.
It was at this time that Kira was faced with the death of Captain Kenji Osagawa, the former commander of the USS Knight. Kira blamed himself for the Captain's death, and as a result of the guilt that he felt, decided to temporarily resign from Starfleet and take a sabbatical on Earth.
His sabbatical was cut short when Kira, along with Lt. Commander Tyran Nige and Ensign Dinara Jin, was reassigned by Commodore Pike to the USS Ronin. At the time of reassignment Kira was given a promotion to Commander, and now serves Captain Ryan Evans as his Executive Officer aboard the Ronin.