Using an Escape Rope here takes you to the inside of Volcano Town Pokémon Center.
(Movement permission; Cross Sea).
Edit: Yes!, I found the sword! thank you for the hints, without them I'd still be at Mt. Skywall. Wow, it's so cool to have Eliza. Now I understand why it was so strong, you gave it Huge Power!
Thanks for reporting,I've fixed these bugs now,also,congratulations for finding the ancient sword.