Attack on Titan: Lost in the Cruel World

"Lost in the Cruel World" is about Mikasa and her relationship with Eren, featuring a vision in an alternative universe where her parents weren’t murdered.

Lost in the Cruel World is a visual novel by Hiroshi Seko. It was first released on September 18th, 2013 in Japan bundled with the third anime Blu-ray. The story was also included in the novel Attack on Titan: Lost Girls which was later adapted into a manga of the same name.