Thoma ages from a boy to a young man through the course of the series. He has typical Nord features: a tanned complexion, blue eyes and wavy brown hair, which he wears tied back with red cord. he wears a deep blue woollen tunic with a cream wavy pattern along the edge (this becomes more of a jacket in his older appearance), as well as cream leggings, leather riding boots with silver caps, a white shirt, green under tunic and a green belt around his waist.
Thoma is considered an incredibly hard worker and has a tendency to prioritise everything and everyone before himself, because he feels that he should set a good example for his little sisters. He is also seen as a great horseback rider by the soldiers at Zender Gate.
Thoma's has an interest in Sharl, the daughter of Marx who runs the inn at Zender Gate. Although their interest is mutual yet innocent, Sharl's over-protective father refuses him to come near his daughter and ask her for her hand, even though he thinks of him as a reliable and thinks of him as a fine young man. Private Hoover likes to tease them, asking Sharl whether they already kissed.
Thoma is introduced as often visiting his interest Sharl at the Zender gate. His sister Sheeda teases them about it, but Thoma is determined to be able to protect Sharl.
Thoma first set foot outside the Nord Highlands when he was invited by his brother Gaius to join him at the Thors Academy Festival. They decided to stay the night before heading to Trista at Sharl's house in Heimdallr. Unaware of Heimdallr's size, Thoma insisted on exploring the city until he and Sharl got lost. After attending his brother's performance, he went to dance with Sharl with whom he came to Trista.
Thoma returns in Nord, now as a young man.
Not content with sitting on the sidelines like he did in the October War, he offers his assistance in tracking down the autonomous tanks and the devices that control them when Nord is threatened to be the site of another war, joining Rean Schwarzer as his companions as they split up into multiple search parties.
Thoma hears a mysterious howl and notices the Simulacrum of Arios MacLaine. Rean tells him to head back to the village while he deals with it. Thoma reaches the village and prepares the horses, but not quite fats enough as the settlement is threatened by bombardment from an autonomous Railway Cannon. At the final second, Rean summons Tyrfing S and blocks the shell, saving the settlement and presumably Thoma. Thoma greets his mother and youngest sister enthusiastically after finding them safe and well.
- Trails of Cold Steel, Chapter 3: "Beyond the Railways", Confidential Synopsis, p.58.