Neti Neti

It's 2055. Eren was injured in a war and sent to the hospital. When he wakes up, he finds out that his arm was amputated and replaced with a prosthetic limb. He and his arm don't seem to be compatible despite the fact that it's the most efficient prosthetic available. His doctor recommends him to therapy, and it turns out that his yoga instructor is none other than Levi Heichou.