Parallel Worlds are alternate worlds that are filled with different realities. For example, parallel worlds are filled with various things not found in other worlds, such as more advanced technology, uncovered ancient civilizations, and medical sciences that can cure diseases labelled to be incurable in other worlds. One individual, Byakuran, the holder of the Sky Mare Ring, can experience all of his other selves' lives and share their information due to possessing the Mare Ring, which has a special miracle that allows the holder of it to do so.
- The theory of Parallel Worlds was first mentioned by Future Lambo during the Lightning Ring Battle.
- Shoichi Irie said that he himself was the cause of Byakuran's power of travelling to parallel worlds awakening.