Thomas H. Norstein is the secondary protagonist in Digimon Data Squad. He is a genius. His partner digimon is Gaomon.
Thomas is a tall teenager with pale skin, straight light blond hair, and light blue eyes. Thomas's civilian attire consists of a dark green v-neck T-shirt, white pants and brown shoes with black soles.
After his memory erased, he begins wearing a white short-sleeved button-up shirt under a green unbuttoned vest, as well as a blue tie, dark blue trousers and brown dress shoes with black soles.
Thomas is a boy genius who graduated from the Stockholm Royal University of Science at the age of 13. His abilities are considered elite, even within DATS. He bases his operations on data and theoretical principles, and as such, his personality clashes with Marcus's. Calm and shrewd, he is the exact opposite of Marcus and sees him as a rival. He has an elitist attitude but he gets emotional when thinking of his mother. Thomas's loyal partner is Gaomon, who always addresses him as "sir" and is easily angered when he thinks someone is disrespecting Thomas.
At first, Marcus and Thomas became rivals in the beginning, but later on became good friends.
When the DATS were pursuing Akihiro Kurata, Thomas pretended to betray the DATS to join Kurata's side, but rejoined the DATS to fight Belphemon.