Nanaba first appears during the 57th expedition as the Squad Leader of Krista's unit. Krista is initially worked up about the Titans who have started climbing the Trees at the edge of the Giant Forest, to which Nanaba calmly replies that if they use their gear to climb further up, it will all be fine. She moves away to another branch and tries to assure the worried Krista that they only have to hold out a little longer, most likely referring to the capturing of the Female Titan.
She is also one of the several soldiers (the others being Gerger, Henning, and Rene) brought by Mike Zakarius to oversee a group of potentially untrustworthy Survey Corps members. The group was assembled close outside of Wall Sina, and disarmed of their weapons due to the suspicion that one of their number might be an accomplice to Annie Leonhart.
Before an investigation can begin, Titans appear within Wall Rose. Nanaba briefly gives in to the shock, fearing that mankind is doomed. However, Mike reminds her that humanity has not lost until they cease fighting and these words restore her resolve to continue on. Afterwards, Mike orders the group to split into four squads to warn the nearby villages. Nanaba's squad searches Wall Rose for a breach, but runs into Gerger's squad coming from the opposite direction without finding anything. As night falls, the two groups take refuge in Castle Utgard.
Castle Utgard soon comes under attack from numerous Titans capable of moving during the night. Since the soldiers who'd been under suspicion don't have Three Dimensional Maneuver Gear, the only ones able to directly engage the Titans are Nanaba, Gerger, Henning, and Rene. However, Henning and Rene are soon killed by a projectile thrown by the Ape Titan, who summons another horde of Titans to attack the castle. Nanaba angrily notes how it seems as though it has only been toying with them the entire time.
With no other options, Nanaba continues to fight with Gerger until their supply of blades and gas is completely exhausted. Injured, Gerger falls from the tower and is nearly caught by a Titan. Nanaba rushes to save him, but runs out of gas and is surrounded by Titans. Both are then devoured, while their charges can only watch in horror.
Nanaba has not been seen much in Action however it is safe to assume she was an Elite of the Survey Corps. Her skills were praised by Gerger as "Superb as always" as well as complimenting Nanaba's skill of very deep cuts.
Her skill in a team is demonstrated later on as well as alongside her comrades having took out 8 Titans which highly impressed Ymir. The fact that she survived the events from 5 years ago, as well as surviving for more than 5 years in the Survey Corps also implies a highly experienced and powerful Soldier.
According to Eld, she was one of the few survivors of "5 years ago", alongside Hange, Levi, Mike and Erwin. Her survival also is said to be the reason why she was among the few who knew about the truth regarding the 57th Expedition and most likely is the reason why alongside Mike, she was watching over the Graduates. At any rate, she was one of the few that Erwin seems to have trusted.