"Akame ga KILL!" is a dark fantasy manga series set in a fictional empire plagued by corruption, inequality, and tyranny. The protagonist, Tatsumi, is a young warrior from a rural village who travels to the capital with his childhood friends to earn money and improve their impoverished lives. Upon arrival, Tatsumi discovers the capital's grim reality: a city rife with exploitation, decadence, and cruelty. His friends are killed, and he is betrayed by those he trusted, leaving him disillusioned and vulnerable.

Tatsumi is rescued by Night Raid, a covert assassination group operating under the Revolutionary Army, which seeks to overthrow the corrupt imperial regime. Night Raid is composed of skilled fighters, each wielding unique Imperial Arms—mystical weapons with extraordinary powers. Among them is Akame, a stoic and deadly assassin who becomes a central figure in Tatsumi's journey. Other key members include Leone, a fierce and loyal fighter; Mine, a sharpshooter with a sharp tongue; and Lubbock, a strategist who uses thread-based weaponry. The group's leader, Najenda, is a former imperial general who provides guidance and tactical expertise.

As Tatsumi integrates into Night Raid, he learns about the empire's atrocities, including the exploitation of its citizens and the use of dangerous alchemical experiments to create monstrous weapons. The empire is controlled by the Prime Minister, Honest, who manipulates the young and naive Emperor for his own gain. Honest's enforcers include the Jaegers, a group of elite assassins who serve as Night Raid's primary adversaries. The Jaegers are led by Esdeath, a ruthless and powerful general with a twisted sense of justice and a fascination with Tatsumi. Other notable Jaegers include Wave, a morally conflicted warrior; Kurome, Akame's estranged sister; and Bols, a kind-hearted but deadly enforcer.

The narrative unfolds through a series of missions and battles, with Night Raid targeting key figures in the empire while facing escalating threats from the Jaegers. The story explores themes of loyalty, morality, and the cost of revolution, as characters grapple with their roles in a brutal conflict. Relationships within Night Raid deepen, but the constant danger and high stakes lead to significant losses, emphasizing the series' grim tone.

As the Revolutionary Army gains momentum, the empire's desperation grows, culminating in a climactic confrontation. The final arc sees Night Raid and their allies engaging in a large-scale battle against the empire's forces, with both sides suffering heavy casualties. The resolution of the conflict brings about the fall of the corrupt regime, but at a great personal cost to the surviving characters. The series concludes with a bittersweet reflection on the sacrifices made and the uncertain future of the empire under new leadership.