A Choice With No Regrets: Preview is an advance of the the visual novel by Gun Snark, A Choice with No Regrets. It was first released on September 18th, 2013 in Japan bundled with the third anime Blu-ray.
Summary
At the beginning, Erwin can be seen exclaiming the words he said to the 104th Cadet Corps during their graduation ceremony: "The majority of the people who stay here and enter the Scout Regiment will likely die. Ask yourselves if you really have it in you to sacrifice your life for humanity".
Erwin disappears to enter the scene the figure of Levi, who speaks the words he said during the 57th Exterior Scouting Mission: "I don't know the answer. I never have. Whether you trust in your own strength... Or trust in the choices made by reliable comrades. No one knows what the outcome will be".
The screen goes black. Erwin's voice sounds saying: "Erwin and Levi. Two of humanity's strongest warriors, how did they meet, and did they come to believe in each other? The past of two people, never outlined before, is now revealed".
Erwin is next seen being pointed by a blade, who then asks: Are you going to kill me, Levi?
It is revealed that the one who points his blade at Erwin is Levi, so he declares that he has joined the Scout Regiment with the aim of killing him.