Green company, the 57th exterior mission part 1

Levi and the special operations squad are said to be humanities greatest and strongest people, years ago there was an even stronger group of people that preceded them with their leader being 6 times as strong as Levi who was a high ranking member in the scouts second in command to Erwin that taught some of the vets everything they know. One day in 845 they mysteriously vanished and were eventually presumed dead. What nobody expected was for them to turn up years later alive and well, the next course of events would drastically change and the leader's friendship with a certain titan crazed section commander would grow into something bigger.