After getting some Ginseng from Lon in exchange for stopping his brother Wong's shady activity, you help Fyda, then you go to Dragoon Castle.
Equip the Speed Shoes
To help you get through Dragoon Castle, you should equip the Speed Shoes. If you don't have the Speed Shoes, get in your ship and sail to the two islands north of Australia. The Speed Shoes are there. When you have them equipped, press X to dash.
Storm the Castle
Leave Yunkou and go west to Dragoon Castle. Perel is there. He will skateboard past the guard. After that, you can go north to enter the castle.
Up ahead, there is a guard with a flashlight. He walks side to side and shines his flashlight all around. If you get caught in the beam of the flashlight, you will be sent back to the entrance. Wait for this guard to stop moving and shine his beam up or down, then press X to dash north past him. Go through the door there.
There is another guard, but he doesn't move. You have to either go to the left of the guard when he is shining the flashlight left, or go right around the guard when he is shining the flashlight right. Once you go north past him, hold Y to run and jump over the gap. Go north and there is another guard up ahead who doesn't move, but shines his flashlight in random directions. Carefully run past him and go through the north door.
You will be in a dark hallway. There are no guards here, so just go west and through the door there.
In this room, press X to dash at the closed door in the north wall. It will open. Go through.
In the next area, there are guards that walk around randomly. You need to go to the northwest door. Go through. You will be in a small room. Go through the door in the north wall.
You will be in the dungeon. Go all the way south to find a Magirock, then go north until you can go east. From there, go north. You'll see Elle chained to the wall!! But then she disappears. Go south and you discover that you have been locked up. Meilin will talk to you.
There will be a cut scene. Afterward, go to the north part of the jail cell and you will hear someone ask if anyone is there. Say yes. Fyda will send a chain down. Go onto the chain and climb up. After you talk to Fyda, leave the room through the south door.
Allow a guard to shine his flashlight on you so you can warp back to the castle entrance. Go in. Go east and up the stairs, then go northeast. This guard is very difficult to get past. You have to just hope that he will walk around so you can get past him. Once you can go past, go through the nearby door.
Carefully go up this hallway where a guard is going up and down. Just wait for the guard to start walking north, and go behind him, but keep your distance because he will sometimes shine his flashlight downward. Eventually he will reach the top and start walking downward. When he does this, hide in one of the side areas until you can run behind him. Do this quickly, because he will stop near there and shine his flashlight side to side. Go through the north door when you finally get past this guard.
You'll be in an area with a big hole in the ground. First, go east. You will have to jump over a bunch of gaps. Go southeast until you are in the southeast corner, then go north and down some stairs. Explore this area thoroughly to get GEMs, a Magirock, an L.Bulb and the 3PartRod. Then go back the way you came until you are back in the room with a big hole in the floor. Go northwest and you will see another vision of Elle. Go north and follow the path to see a cut scene. After this, Fyda will follow you. Go back the way you came. You will find Meilin at the bottom of the room. Talk to her. You seem to be trapped again, but Perel busts open the door. After Perel and Fyda leave, talk to Meilin for a hint about finding the Princess. Then go through the door that Perel opened.
Return to the castle entrance (just let a guard catch you) and go inside the castle. Then go to the left, where there are some stairs. Go up, then go northwest and go through the door there.
In this room, throw pots at the candles to blow them out. Then a door opens in the north wall. Go through.
You see a statue in this room. Go to the wall across from the statue and check on the wall. You will notice a switch (but if you didn't see the cut scenes in the east side of the castle, you won't see the switch). Push it, then go north and through the door that opened. In the next room press X to dash at the door with the Speed Shoes, then go through.
Go up and talk to the Princess. Watch the cut scenes. Leave the room, then you encounter Meilin, who says she'll show you the secret exit. Go to the northwest of this room and go through the door there.
There will be a cut scene. Follow the path and some more cut scenes will occur. Eventually you will be outside the castle and Perel says to visit Will at Nirlake. So go south to leave the castle. Go to the dock and sail to Freedom, then go north to Nirlake. Go to Will's house in the northeast and talk to Will.
Now you can go south to the runway next to Freedom. Walk onto it and press A. Fly to Mosque, which is the only other place in the world where there is an airplane runway. Use the L and R buttons to descend to the runway, then press A to land.
Go north to Mosque and you can talk to the people to find out more about this Beruga guy. There is also a Magirock in one of the houses, and you can buy things at the shop or sleep in the inn.
Be sure to go east from Mosque and you can go over a bridge into the snowy area. There is a cave northwest of the bridge where you can get the BlockRod.
Then when you're ready go south from Mosque to reach Beruga's Lab.