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 with a small-time gang. His life wasn't going anywhere until Erwin recognized him from an MMA video on YouTube. He picked Levi up and got him a position at Trost as one of the founding members of the MMA club. Later, Hange convinced him to get a TA position to fill the hours and distance himself from martial arts while he got his life back on track. Eventually, Levi upgraded himself to become a full-fledged high school teacher.

• Levi's primary position in Trost is still as an MMA instructor. His students refer to him as "Captain" or "Heichou" because of his teaching style. He's in charge of training a handpicked group of students to represent Trost in official competitions. They're called "The Wings of Freedom".
• Keith Shadis Self Defense Academy doesn't have belt levels or specific curriculum. Levi conducts his MMA program the same way. For formality's sake, The Wings of Freedom are classified as Black Belts.
• Levi's sparring stance is his own twist of traditional stances. Aside from common MMA disciplines (e.g. karate, kickboxing, muay thai), Levi is also familiar with more obscure ones developed in Asia, such as eskrima and bartitsu.
• He chose to (get a degree in and) teach physics because it came naturally to him. He applies his knowledge of physics to MMA.
• His physics students have (un)officially nicknamed him as "Humanity's Strictest" because of numerous threats of bodily harm involving scientific instruments. He also punishes students with detention and cleaning duty.
• Oluo is Levi's TA, and Eld is the other physics teacher who takes over Levi's classes when he's away for competitions. Hange teaches biology and chemistry. Petra teaches world history.