Alex Rossa, a 21-year-old sergeant in the Allied Forces during World War II, specializes in combating the werewolf threat known as Loup-Garous. As the son of an expert hunter, he mastered survival skills, combat techniques, and marksmanship, making him exceptionally proficient with firearms and tactically resourceful.

Physically, he operates at peak human strength and speed, with above-average stamina. His durability—rated "wall+"—allowed him to survive direct assaults and a Loup-Garou bite. He consistently wears his nation’s khaki uniform and beret, wielding dual compact pistols with ambidextrous skill.

Rossa’s very high intelligence supports his strategic capabilities and rank. He demonstrates rational thinking and adaptability, crafting improvised devices like a makeshift time-bomb to destroy a cabin. As a sergeant, he recruits and oversees personnel, including cryptanalyst Testa Lielbelle for missions targeting werewolf communications.

He shares a history with Testa as his boarding school senior and maintains a protective bond. During a critical mission, Rossa deliberately engaged Lance Corporal Blake to enable Testa and werewolf Yonaga’s escape, nearly dying in the process. Testa intervened in wolf form to save him. Afterward, Rossa gave his hat to Testa to conceal wolf ears, then received medical aid from Allied personnel.

His motivations center on minimizing casualties on all sides and swiftly ending the Loup-Garou war, driven by duty and deep care for comrades, especially Testa.