Attack on Titan: Counter Rockets S01 E01 The Strike Back Begins

Soldiers are engaged in training and developing weapons for the fight against the Titans. One day, Izuru is sent from the Public Security Command Bureau and meets Hange who has been researching the ecosystem of the Titans. She is secretly advancing studies on the Titans in her own research lab. Developing an interest in Hange, Izuru infiltrates the lab and learns that a Titan which was successfully captured, is sequestered in there.