People need body parts to go far in their life. Both for doing something and to lives. Although, they can still live without their limbs, sight, earring and voice. But they can't live without vital body parts, namely the head and/or torso. Everyone knows that.

In this story however, everyone can live without a specific body part including the vital one. But when the body part is separated from its host, it become its own being. In other case, they can move like it had a complete body, sometimes coupled with another body part. And another one when a person was born as a single or multiple body part.