Go to vedan when you unlock it and go to the item shop where you get the mining license and battle the people in the area and heal your people by walking on the transporter there also if you use jasters desert storm ability if your person is strong enough it should pretty much kill them in one hit this will make you money and experience quick.
Ghost Ship Extreme level
Use the Key of the Underworld.
Ghost Ship level
Complete the game, and save when prompted. Now go to your ship and look at the map, you will see the new level.
Key of the Underworld
Answer the questions in the Seventh Mystery correctly.
Kisaras Swimsuit
Complete Ghost Ship Extreme.
New Game Plus
To unlock all previously obtained costumes into a new game, simply hold R1 while hitting the new game option from the title screen.