Soushi has light brown hair over his shoulders and tied at the end. His fringe is usually swept to the left slightly, he has light brown eyes, the left of which has a diagonal scar from an accident. He wears the standard uniform.
Soshi carried the heavy burden of knowing the truth at hand. This related to his unique job which also left him somewhat isolated leading some people to note him as awkward. He ensured he remained calm and rational when guiding the other mechas, so as not to cause their pilots to experience doubt. Soshi also showed he cared about people and made efforts to help them. His attitude was firmly committed to assisting in the fight against the hostile Fafner.
Soushi is the only one of all the children on Tatsumiya Island who knows the truth—the world has been under invasion by an alien race called the Festum for the past three decades after Japan was destroyed over 30 years ago. He is the son of Minashiro Kouzou, the commander of the secret military fortress Alvis, which is hidden in the bowels of the peaceful-seeming Tatsumiya Island. From a very young age, Soushi was bred to become the next commander of Alvis, so he has had a very isolated childhood carrying the heavy secret of the war and being told day in and day out that he must live only to protect the island.
Because of his years of virtual isolation, he is rather awkward socially, (in fact, most people find him quite unapproachable or mistakenly think him hard-hearted). Kazuki alone seems to make efforts to understand and befriend him and the two become very close over the course of the series despite an unfortunate incident between them that occurred when they were younger.