Complete story — includes the ending
In the past, Christa and Ymir became lost in a blizzard during their winter training in the mountains while trying to save fellow cadet Daz. Ymir accused Christa of having a death wish rather than saving Daz for selfless reasons. She was aware that Christa is the illegitimate daughter of a nobleman's mistress who was forced by the Wall Cult to change her name and join the army to avoid disgrace. Ymir made Christa promise that she must live life on her own terms if she ever reveals her true name. In the present, Ymir transforms into a small intelligent Titan, fights off the other Titans, and saves everyone. Just as the Titans overwhelm her, Hange and the other Scouts arrive in time to save her and the 104th Cadets. Before the gravely-injured Ymir loses consciousness, Christa reveals that her real name is Historia Reiss.
Sources and content license
Source and revision history · Adapted from Wikipedia contributors, Attack on Titan season 2. Reference markers and HTML formatting removed. · Content license