"86" is set in a war-torn world where the Republic of San Magnolia is engaged in a prolonged conflict with the neighboring Empire of Giad. The Republic claims to fight using autonomous drones, presenting itself as a technologically advanced and casualty-free nation. However, this is a facade. The drones are actually piloted by humans, specifically the "86," a marginalized group of people deemed subhuman and forced into military service. The 86 are descendants of those who were not of the Republic's dominant Alba race, and they are systematically oppressed, stripped of their rights, and sent to the frontlines to die.

The story unfolds through the perspectives of two main characters: Vladilena "Lena" Milizé, a noble-born officer in the Republic's military, and Shinei "Shin" Nouzen, a skilled 86 pilot known as the "Undertaker" for his ability to sense the deaths of his comrades. Lena is assigned to command the Spearhead Squadron, a unit composed entirely of 86, through remote communication. Initially, she is idealistic and naive, believing she can treat the 86 as equals despite the systemic discrimination they face. Over time, her interactions with Shin and the squadron reveal the harsh realities of their existence and the Republic's hypocrisy.

Shin, on the other hand, is a battle-hardened veteran who has lost countless comrades and carries the emotional scars of war. He is deeply cynical about the Republic and its promises, yet he continues to fight, driven by a sense of duty and a desire to protect his fellow 86. The relationship between Lena and Shin evolves as they navigate the moral complexities of war, loyalty, and survival. Lena's growing empathy and determination to challenge the system contrast with Shin's resignation to their grim fate.

The narrative explores themes of systemic oppression, dehumanization, and the psychological toll of war. As the Spearhead Squadron faces increasingly dire battles, the story delves into the personal struggles and camaraderie of its members, highlighting their resilience and humanity in the face of relentless adversity. The Republic's lies and the true nature of the conflict are gradually unveiled, culminating in a confrontation that forces both Lena and Shin to confront their beliefs and the world they inhabit.

The series is notable for its intricate world-building, blending futuristic technology with the grim realities of warfare and societal inequality. The characters are multifaceted, with their motivations and growth central to the narrative. The story balances intense action sequences with poignant moments of introspection, creating a compelling and emotionally resonant tale of survival and defiance.