Attack On Titan: Before The Fall 10

With Kuklo's fate unknown, Sharle has to take matters into her own hands by tracking down the reclusive Angel, inventor of the Device that could one day be the difference between survival or extinction at the hands of the Titans. But Angel is no longer the same man he once was, and the journey to reach him will be a perilous one, to say nothing of actually enlisting his help…

Volume 10 of the Attack on Titan: Before the Fall manga series by Ryo Suzukaze.