Eugene Sevenstark is a central character in the events of Mobile Suit Gundam Iron-Blooded Orphans. He begins as a boy soldier in the Chryse Guard Security (CGS), a precarious position common to many of the orphans on Mars who must fight to survive. Before the arrival of Orga Itsuka, Eugene was the leader of the CGS's Third Group of child soldiers, a position that created a foundation for their early rivalry.

Physically and intellectually gifted, Eugene is a courageous and talented individual. However, his personality is marked by a certain impulsiveness and a lack of patience, which can initially make him seem somewhat unlikable or abrasive to those around him. He is notably straightforward and does not hesitate to voice his pragmatic, if sometimes cold, opinions. Unlike the more hot-headed Orga, Eugene possesses a rational mindset and is capable of making the difficult, cold-hearted decisions necessary for survival, such as when he insisted the Tekkadan ship not risk immediate destruction to retrieve a fallen comrade’s body. Despite his rough exterior and tendency to clash with others, he is fiercely trustworthy and deeply loyal to his friends and teammates. His primary motivation is the protection of Tekkadan and its members, a goal he pursues with a pure and endearing dedication.

Initially resentful of Orga Itsuka for taking his place as the de facto leader of their group, Eugene frequently rebelled against him. However, after the formation of Tekkadan, this friction evolved into a profound mutual respect. Orga came to recognize Eugene's remarkable capabilities, particularly his aptitude for ship command, and entrusted him with immense responsibility. This trust culminated in Eugene becoming the Deputy Leader of Tekkadan, often taking command of missions and the group's motherships when Orga was unavailable. Eugene's bond with fellow pilot Norba Shino is particularly significant; they are childhood friends who constantly bicker and fight, yet their deep care and strong teamwork on the battlefield are undeniable.

The character undergoes substantial development throughout the story. As the weight of responsibility grows, the impulsive boy matures into a dependable leader. He actively studies tactical guidebooks to better support Orga and lighten his leader's burden, showing a commitment to his role beyond just combat. After the death of Biscuit Griffon and the increasing pressure on Tekkadan, Eugene's role as the steady second-in-command becomes more crucial. Following the tragic death of Orga, Eugene steps up as the unofficial leader for the remaining members, giving the orders to evacuate and ensuring that some of Tekkadan survives the final conflict. His pragmatic rationality serves the group well in its darkest hours.

Eugene possesses a notable suite of abilities. He is a decent Mobile Suit and Mobile Worker pilot, capable of providing effective support fire in battle. However, his most exceptional skill lies in his use of the Alaya-Vijnana System, a neural interface implant. Using this system, he is a genius-level pilot of armored assault ships. Orga placed immense trust in Eugene's ability to command the Tekkadan flagship, the Isaribi, and Eugene proved his mettle by performing incredible feats of piloting. His most acclaimed achievement was simultaneously piloting two ships, the Isaribi and the former Brewers’ vessel Hammerhead, to evade the entire Gjallarhorn Outer Earth Orbit Regulatory Joint Fleet—a feat no one had ever accomplished before. In the years following Tekkadan's disbandment, Eugene survives and continues to honor the group's legacy, becoming a bodyguard and personal assistant to Kudelia Aina Bernstein, the advocate for Martian independence.