Shingeki! Kyojin Chuugakkou - episode 2 - 10 Oct, 2015

Eren’s homeroom teacher tells him that he needs to go collect the club admission form from Armin Arlelt who has been absent from school. On his way to Armin’s house with Mikasa, they encounter an upperclassman who defeats a Titan with a single blow. (Source: FUNimation)