Credence raised his hand and massaged his stiff neck. He held that posture for a long time as he stared at the white wall that was connected to the delivery room. His neck was as stiff as a board. It felt numb, sore, and was quite painful.

But the pain was nothing to him. He could tolerate it.

But on this day, the strain from the gruesome rehabilitation training had begun to spread from his arms to his thighs, torso, and gradually, his entire body.

It felt like his muscles were being stabbed with a knife. It was so painful that he, a man who used to train in the...