K-2SO is the droid guard of the KX series, originally created for the armed forces of the Galactic Empire. Like all droids, it could function in a vacuum (in outer space).
At some point, the droid joined Captain Cassian Andor, a member of the Alliance for the Restoration of the Republic, a rebel movement seeking to overthrow the Empire and restore democracy. Andor managed to reprogram K-2SO as a strategic planning specialist for the Alliance service.
Together with the rebel group K-2SO, he participated in the mission of stealing the drawings of the Imperial Battle Station, the Death Star. During the mission, Kay-Tu was destroyed by the Empire's attack aircraft when he covered Cassian Andor and Jean Erso, who were looking for a data carrier with drawings in the Citadel.