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 storyline in which the Colossus Titan never attacks, the 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 outside the walls and Mikasa wakes up, being a dream just after Mikasa falls out of gas in the Trost Battle.

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

Wall Sina, Goodbye
Written by Hiroshi Seko. Set on the last day Annie spent in Wall Sina before her attempt to capture Eren inside the walls. In this story Annie has to find the daughter of a local merchant. In the end, Annie takes a shower promising that the next day will finish everything and capture Eren.

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