Oni / Ki
By itself it's Oni. But when the kanji appears in combination with other kanji, it tends to be shortened to Ki. This can be seen best in the naming of the Hibiki Oni, where all the Oni's names end in -ki.
It means "demon", "ogre" or "spirit of a deceased person".
In myths, they are often said to live on an island called Onigashima which literally means "Oni island".
- Kamen Rider Hibiki
- Kamen Rider Den-O
- Chou Kamen Rider Den-O & Decade Neo Generations: Warship of Onigashima