Setback at the Initiation

Setback at the Initiation (経始の躓石) is the 1st chapter of the 15th volume and the 53rd chapter overall of the Attack on Titan: Before the Fall manga, written by Ryō Suzukaze and illustrated by Satoshi Shiki.

Overview
Rosa and Kai manage to pass the secondary aptitude test while Felix does not. As Rosa apologizes to her friends for her recent behavior, Kuklo and Cardina are glad the group's morale has improved to where it previously was. Later, they discover that the next batch of vertical maneuvering equipment will be the last, along with Rosa's natural talent with using the gear. However, while practicing with a Titan dummy, it is discovered that Rosa's gear has been sabotaged by an unknown party.

Summary
Rosa manages to pass the test, much to her relief. Kuklo congratulates her and then calls up Kai to take the test. Both recruits share a few words before Rosa goes to Felix and apologizes for her outburst earlier. Before Felix can say anything, Rosa promises to give him a proper apology later and departs.

That night, Kai proclaims a toast for him, Rosa and the others who passed the secondary aptitude test, not realizing that none of his friends feel like celebrating due to Felix not passing. They try to placate him by saying there is the third test coming up and Rosa formally apologizes to all of them for her behavior, especially to Felix who tried to help her. Felix smiles and accepts the apology, noting how Rosa managed to overcome her fears but still doesn't think she should battle against the Titans. Rosa says she is going regardless and claims she has found her own reason for joining, not out of vengeance or to avenge her father Sorum; Felix stuns them all by saying his reason for joining is to protect Rosa, greatly embarrassing Rosa and causing her to blush uncontrollably. Kuklo notices they are all on speaking terms again; Cardina agrees and mentions that it helps with the general mood, with that group in particular standing out when compared with the others. With the ones who passed the test that day, that leaves eight who have yet to pass and Cardina states they will need to improve their training methods to make sure all seventeen will be ready by the time the expedition is set to begin.

The following day, Carlo takes the nine members who have passed to the forest to practice once more with the vertical maneuvering equipment. As Carlo gets Hugo, Kurz and Ivo ready to go, Rosa volunteers to try first. Remembering how Kuklo operated the device, Rosa fires an anchor and successfully navigates through the trees and lands on a branch. Cardina and Carlo are surprised Rosa managed to do it in her first attempt and notice that she acted similar to Kuklo; the latter mentions that Rosa is well proportioned and her reflexes are excellent but that she may have trouble with the strength of the swords. Carlo inquires about the production of the equipment and Angel reveals that Xenophon went to the other workshops for assistance, but the next shipment will use the last of both the funds and materials set aside by the Military Police.

After the last eight recruits pass and receive the last shipments of vertical maneuvering equipment, Carlo reveals the training dummy Kuklo and Cardina used during the initial tests. Kuklo splits the recruits into two teams to practice attacking the target, with the recent eight recruits following Cardina to the rear of the target. After Kuklo demonstrates how to attack it, Rosa once again volunteers to go first. However, Rosa discovers a problem with her gear while looping around to attack the target and gets knocked unconscious; after Sharle inspects it, she discovers the gear was sabotaged and the harness was scored by a knife.