All basic information based on Levi's Wikia page.

Back story based on A Choice With No Regrets/Birth of Levi, a Levi-centric spin-off written by Gan Sunaaku and illustrated by Hikaru Suru. It's based on the visual novel of the same name.

Levi grew up in the Imperial Capital's Underground City, a district located beneath Wall Sina. It was initially developed in the event of Titan invasion, but the project was abandoned. The remaining structures are now occupied by criminals and the poor. Reconstruction by the inhabitants made the Underground City dangerous for the Military Police to enter. Needless to say, it's a lawless and desolate place, a contrast to the prosperity aboveground.

• Levi has no family. Instead, he has allies. The closest he had to friends before the Survey Corps were Isabel and Farlan.
• The 3DMG they used was acquired from the black market or stolen from soldiers who ...

Back story based on Knockout, a martial arts AU fic written by Raylou.

The MMA aspect of this AU was inspired by Hajime Isayama's love for MMA, as seen in the fight sequences and the slender figures of most of the characters. After reading Knockout, it was a no-brainer on my part. The teacher bit was more of an afterthought--a day job or cover for Levi when he's not teaching MMA.

Similar to canon, this Levi grew up in a bad neighborhood, but he had good parents. They sent him to Keith Shadis Self Defense Academy, so he can learn how to protect himself from an early age. He was a prodigy and he topped nationwide competitions in sparring. Thanks to social media, he gained a following over the years. He also established and lead the martial arts club in his high school.

His parents passed away when he was eighteen. He became a delinquent and fell in w...