An ajin is a creature that cannot be seen or heard by all creatures and humanoids except those that own one. Some ajin simply do whatever they want, while other owners can command their ajin properly and share their ajin's field of vision and command it to attack targets. Some ajin are reckless and attack anyone in their immediate vicinity. Ajin also seem to have a will of their own and are shown to be quite intelligent. Ajin often mimic the core personality of their owner.