Mina appears in Ch. 3. When the Colossal Titan appears outside Trost District, the burst of steam from its body knocks a number of trainees off the Wall. She follows when Eren instructs the other trainees to attack the Colossal Titan. After the second attack of the Colossal Titan, she was assigned to the middle guard along with Eren Yeager and Armin Arlert. Initially tasked with working under the training corps, they eventually were incorporated into the front guard due to the number of titans. Catching the group unaware, a titan lunged at the roof top they were standing on.
When Eren was talking about how killing titans that got in Trost District will get their rank up high, she joined him indicating that she is also signing up for Scouting Legion.