In a 104th training exercise, the cadets notice that three people are missing. In the blizzard, Christa drags Daz through the snow. Ymir realizes that Christa is an illegitimate noble, and sends her ahead whilst she takes Daz. At the base, Christa finds the others had miraculously survived.
At Utgard, Ymir engages the Titans. During the fight, she tears down the tower, and rescues the other recruits. The Titans later emerge from the rubble, and begin to devour Ymir, until the Scouts arrive and cut them down. After the battle, Christa tells Ymir her real name – Historia.
You can watch Attack On Titan Episode 30: Historia online for free in the next link: