How to unlock Explorer Shores?

[Diamond Sutra]

Hey all, I've completed the game; and I'm looking to check out the other explorer shores that I see in guides. I can't see the last three islands (Coral Cay, Unholy Helm, Defiled Isle) on the map. It's not that they are showing but "locked", they are simply not showing up at all.

How do I get them to show up? I checked many online guides but they are all focused on what to get when you arrive on those islands, nothing about how to make them appear on your map.

Thanks!

[Diamond Sutra]

Ah, nevermind, I had one last thing to do (rescue shiro-ji; the last three islands unlock on the map after he gives you the instructions to the Builder's Hammer).