Attack on Titan: No Regrets volume 2, a prequel to Attack on Titan, features story by Gun Snark and art by Hikaru Suruga.

Erwin's political enemies have hired Levi and his crew to take back some incriminating documents. Their reward: the right to live a proud life above ground, in the royal capital. But deep in Titan territory, it's going to be tough to break formation and steal from a squad leader, and Levi still insists on killing the man who humiliated him after the mission is complete. Of course, beyond the walls anything can happen, and a sudden change in Levi's fortunes will force him to face the greatest regret in his life...