Leonhart "Leo" Saijou, a Class 1-E Course 2 student at First High School, shares courses with Tatsuya Shiba, anchoring one of the protagonist’s rare male friendships. Born to a half-Japanese father and quarter-Japanese mother, his mixed heritage echoes in his foreign-sounding name and striking auburn hair paired with vibrant green eyes. Standing at 1.80 meters with a lean, athletic build of 75 kilograms, his physicality complements his explosive combat style.

Leo’s hot-blooded impulsiveness and quick temper contrast his unwavering loyalty and camaraderie. A natural athlete, he wields Fortification Magic to amplify durability in allies or structures, blending raw power with tactical support. During the Watatsumi rescue operation, he confronts USNA STARS operatives Ralph Algol and Ralph Hardy Mirphak in fierce combat, backed by Katsuto Juumonji’s reinforcements—a testament to his battlefield tenacity.

Beyond combat, Leo engages in First High’s Extracurricular Activities Federation, though the scope remains undisclosed. His dynamic blend of fiery resolve and steadfast friendship cements his role as both a trusted ally and formidable force.