Katie

"Aloha!" - The sound of Katie's throat

Katie is the protagonist of Portugal. She is a prisoner and test subject of the Aperture Computer Assistance Center, where she is guided by her sister Gladys in a series of tests involving the portable portable portable device. According to Gladys, both her and Katie are dead.

Among the living
Based on "Aloha!" being the sound of her throat, it is possible that Katie is from Polynesia.

At some point in their life, Katie and Gladys' father rented a firepit. Around this time, Gladys said "Hello," but Katie responded with "No." Gladys then kills (or at least is accused of killing) Katie. Gladys probably "died" around this time as well.

Either before or after their death, Gladys and Katie may have been romantically involved, though it appears that they both cheated on each other.

Post-death
After supposedly dying, Katie wakes up in the Aperture Computer Assistance Center, where the events of Portugal take place.