Aboard the Nautilus
Once on the ship, Seth brings everyone up to speed on Gongora's movements. Kaim agrees that to find him, it would be better to track Grand Staff than to return to Uhra. They decide to pick up new supplies before looking for Grand Staff itself, which includes a way to make the Nautilus stronger.
Meanwhile, Ming helps jar the memories of the other immortals. There is a place, somewhere, called the Hall of Mirrors where the other four confronted Gongora. The four allies agreed to leave the world, but Gongora insisted on stayed. He found out that as long as the mirrors are there, and as long as they are in the world, magic energy will keep increasing. He wants that power, and doesn't want to go.
The allies try to reason with him, but it does no good. He casts a sleeping spell on them, promising them all (especially Kaim) that they would understand eventually. Because Ming passed out then, naturally she doesn't know what precisely Gongora meant either. This was 30 years ago, right around the time of the Magic-Industrial Revolution. Definitely not a coincidence.
You get control of the Nautilus then, and have an incredible amount of freedom for the first time in the game. There are many things you can do here (dreams, side quests, etc.), but we're going to concentrate on the story for this portion of the guide. We'll alert you when the last chance is to finish up all your side quests before the final dungeon, but know that for now, you're pretty free to do what you want.
To get to the eastern continent, you need to take a rather roundabout way. If you simply go south as Kaim suggests, you're going to smack into the hypercurrents and be unable to proceed. Instead, you need to southeast to go around the hypercurrents, then come back west toward the island. Keep an eye on the map, as the large flashing dot is your target.
You're tasked to get into the inland lake. To do that, go to the northern tip of the island, then dive underwater. A thin passage will lead you to the lake, despite it being landlocked. Surface, then disembark.