Attack on Titan: Lost Girls (Novel)

Attack on Titan: Lost Girls (進撃の巨人　ＬＯＳＴ　ＧＩＲＬＳ) is a Japanese novel and compilation of three stories written by Hiroshi Seko, who worked as a scriptwriter for the anime. It is based on the visual novel of the same name, released on the Blu-ray copies of the anime, with the addition of a new one, Lost Girls, which details Annie and Mikasa's relationship in the training days. Mikasa wonders why Annie acts the way she does and what burden she carries. The three stories were also adapted into a manga of the same name.

Lost in the Cruel World
Written by Hiroshi Seko and set in an alternative reality in which the Colossus Titan never attacks, Mikasa's human traffickers are killed by wolves and Mikasa's mother is pregnant which prompts the multiple visits by Grisha Yeager to the Ackerman family. Mikasa and Eren quickly become friends. Proving their friendship, Eren vows to see the outside world, to be able to see beyond the walls he uses an airplane built with Armin's help. In the end Eren dies when the airplane crashes before properly taking off and Mikasa wakes up, being a dream just after Mikasa falls out of gas in the battle of Trost.

The visual novel version was released on September 18th, 2013 in Japan and bundled with 3rd anime Blu-Ray release.

Wall Sina, Goodbye
Written by Hiroshi Seko. Set on the last day Annie spends in Wall Sheena before her attempt to capture Eren in the 57th expedition beyond the walls. In this story Annie has to find Carly Stratmann, the daughter of a local merchant.

The visual novel version was released on December 18th, 2013 in Japan and bundled with 6th anime BD.