You had been anticipating this all day. The signal.

The moment the commanders hand raised, you didn't hesitate. You bit your hand, and a flash of lightening appeared where you once were.

He was the only one who knew. Before now, atleast. You'd be damned if you let any more of your comrades die because of your own selfish fear. You'd help. You'd prove yourself as a soldier, and to Erwin.

Had you truly gone insane and dedicated your heart to such a man? Yes. Without any shame.