Hamil serves as a major in an alien military force embroiled in interstellar warfare. Reporting directly to Colonel Fomalhaut, commander of the space army, her core objective is locating and recruiting Oji Tanaka—a former rock musician codenamed "Gabriel"—whose electric guitar performances generate power for their ultimate weapon. Her mission requires coordinating Oji’s guitar activations to deploy this system against enemy forces. She operates undercover on Earth, posing as Oji’s coworker in his office building to facilitate her assignment while contending with Colonel Fomalhaut’s skepticism about Oji’s capabilities, compelling her to conduct additional evaluations.

Demonstrating steadfast dedication, Hamil reforms Oji’s old band "Black Heaven" to harness their collective musical synergy for maximum weapon efficacy. She commands three subordinates—Kotoko, Eriko, and Rinko—for Earth operations, though their misguided attempts to provoke intimacy between Hamil and Oji (believing it essential to trigger his powers) create friction with Oji’s wife. Hamil’s interactions extend to Oji’s family: she visits their home under the pretense of research, inadvertently fueling Yoshiko’s suspicions of an affair, and encounters their son Gen, who links her to a space-themed TV character. When Gen accidentally boards an alien vessel during a mission, Hamil oversees weapon deployment against attacking foes while Oji rescues him.

Calm, wise, and deeply versed in music’s strategic role in the conflict, Hamil mentors Oji through his responsibilities. She maintains professionalism while navigating human complexities and wartime pressures, ensuring repeated successful weapon activations through Oji and Black Heaven’s reignited artistry—directly influencing the war’s trajectory.