One Piece Encyclopedia
| Impel Down | It is an underground prision located in the governmental island, Enies Lobby. Here it is where the most dangerous criminals of the world are sent. |
| Island Kujira | A type of whale from the "West Blue". They can reach the size of an island, hence their name. They usually travel in whale groups or gam. |
| Isshi-20 | When Wapol exiled all the doctors from Drum, he choose a group of selected doctors for his personal use, that group is called the "Isshi-20". All citizen who needed be taken care of doctor must go to Wapol and suplicate that they cure him. |
| Ittouhei | "First class private recruit" - A person recruited by marines to exert as soldier. |
| Ittouryuu | Ittouryuu is a sword discipline that consists in using only one sword. |