After the battle of Shinganshina, most of the Titans were defeated but to the cost of many lives... so many soldiers had fallen. This was the harsh reality for the Survey Corps but this wasn't fully over yet.

Perched on a roof, Eren frantically tried to keep burned Armin alive, he begged Levi to save his friend's life with the Titan serum. He agreed, but was then stopped by the arrival of Floch, carrying the near-lifeless Commander, Erwin Smith. Seeing that Erwin was barely but still breathing, the Captain announced to you that he had changed his mind, and would instead use the serum to save the Commander...

You, Eren and Mikasa objected. After all, Armin has done more for the Humanity in the course of this battle than Erwin... and the fact that Floch, the surviving recruit, believed that the Commander deserved another chance, didn't help at all.

As Levi gripped tight the serum and he spoke once again, "I am doing the injection on Erwin. Get out of my way."

Suddenly, Mikasa didn't hesitate to draw her weapons against the Captain, lunging at his direction. She held him down, blade to his neck and pinned on the roof.

It was an unthinkable situation to see soldiers rise up against their superiors...