From Bulbapedia, the community-driven Pokémon encyclopedia.
Sevii Isle 8 (Japanese: ８ばん ななしま 8th Seven Isle) and Sevii Isle 9 (Japanese: ９ばん ななしま 9th Seven Isle) are routes which are not accessible through normal gameplay in Pokémon FireRed and LeafGreen. However, unlike other similarly-named unreachable areas, they have actual map data. Their Japanese name is the same as that of the Sevii Islands but it is instead spelled in hiragana (なな) as opposed to the latter's usage of katakana (ナナ).
No Pokémon are programmed into the areas by default; it seems as if there are abandoned areas left over from the development period of the games. No index pointers lead to it by default either; on Sevii Isle 8, the central island on the route has what one would assume to have been cave entrances changed into the side of a rock.
If it is entered when walking on land, it has the same route theme as the later Sevii Islands routes. If the Town Map is opened at Sevii Isles 6, 7, 8, or 9, it displays the player's location as if they were near Four Island. Additionally, their index numbers are located after Three Isle Port and Resort Gorgeous, where routes on Floe Island may have been located.
There is also location name data programmed in the games for the following locations:
- Sevii Isle 6 (Japanese: ６ばん ななしま 6th Seven Isle);
- Sevii Isle 7 (Japanese: ７ばん ななしま 7th Seven Isle);
- Sevii Isle 22 (Japanese: ２２ばん ななしま 22nd Seven Isle);
- Sevii Isle 23 (Japanese: ２３ばん ななしま 23rd Seven Isle);
- Sevii Isle 24 (Japanese: ２４ばん ななしま 24th Seven Isle).
However, they have no map data. Sevii Isles 22, 23, and 24's location name data are located between the Tanoby Ruins and Navel Rock.