Attack on Titan volume 21 features story and art by Hajime Isayama.

Locked in a desperate battle with humanity's most terrifying enemies - the Colossus, Armored, and Beast Titans - the survey Corps gets closer than ever before to Eren's basement and unlocking the mysteries of their walled world. But to get there, they will have to make a terrible choice with life-alerting consequences for every surviving human soldier...