The Margin of Error

In the Recon Survey Corps Division, emotions are a risk.
There, agents are conditioned to execute orders without thought, assassinate without emotion, and never, ever get close to others.
Levi Ackerman learned this lesson at an early age-and he has adhered to it religiously in his life to date.
Until Erwin Smith.
As a commanding officer, Erwin was never intended to be anything more than his superior. But after years of working together, something occurred between them that no amount of rank could suppress-a bond that was born of silence, tempered in trust, and tested in, at best, each mission that they barely made it through.
Then was the blunder.
The blunder that resulted from one miscalculation, one miscalculation that cost lives that should never have been taken, and brought a rift to their partnership.
Levi took the fall to protect Erwin's honor, and in exchange, Levi lost his MO, his career, and the man that he could never have.
Months later, Levi is brought back under the command of Erwin for a covert mission.
The rules have not changed: follow orders, complete the mission, and have no feelings.
But from the first moment their eyes met again, every rule started to unravel
Now Levi has to choose between the duty that formed him, the many years of hard work, and the man who shatters him by simply breathing.
Because in the Recon Survey Corps Division, crossing the line isn't just against the rules.
It is treason.