Luke Walker is an American military instructor stationed at Watcher's Nest. He trains the Seraphim cadets—Misaki Kureha, Luxandra Frail, Suzanna Bluestein, and Kiri Marialate—under Lyar Von Ertiana's command, continuing their instruction after their base arrival. Walker approaches training with strict fairness, pushing cadets beyond their tolerance to build resilience. He refuses to act as a "babysitter," halting training for unmotivated trainees like Misaki during her struggles until they recover independently. An inconsistency exists regarding his military rank: identified as a chief petty officer in-series dialogue yet listed as sergeant in the opening credits' official biography. No concrete information exists regarding Luke Walker's background, personal history, character development, or specific plot involvement across official media, including the original *Divergence Eve* series and its sequel *Misaki Chronicles*; his documented role remains strictly that of the cadets' military instructor.