Juujika no Rokunin

To stand against monsters, one must first abandon their own humanity—a truth that sixth-grader Shun Uruma learns in the most brutal way imaginable. Branded as "Specimen A" by a clique of five sadistic classmates, Shun endures relentless torment that transforms his school days into a waking nightmare. The only light in his abyss comes from his loving parents and his devoted older brother, who provide him with fleeting moments of warmth and safety. But that fragile peace shatters when the five monsters, having escalated their cruelty beyond any conceivable limit, slaughter his entire family before his eyes. Stripped of everyone he holds dear and plunged into the absolute depths of hell, a singular, searing wish ignites within Shun's hollowed heart: vengeance, at any cost. Rescued from the brink by his grandfather—a grizzled veteran of a covert WWII military unit—Shun is subjected to years of grueling, merciless training designed to forge him into a weapon of pure retribution. His body is honed, his mind sharpened, and his humanity systematically stripped away until nothing remains but the cold, focused instrument of his dark desire. Four years pass, and the innocent boy who once cowered before his tormentors is no more. Emerging from the shadows, Shun finally comes face to face with his fated enemies, now older but no less monstrous. With a gaze devoid of mercy and a conviction that brooks no obstacle, he delivers an unyielding declaration: nothing, and no one, will stand between him and the bloody annihilation he has sworn to deliver.