The things you need for this task are:
1. Pokemon has the ability to fly or swim to move from island to island
2. Pokemon have the ability to open pits
3.100 worms (can be obtained from nidoking and nidoqueen or other sources)

Note: You will lose 6TD to buy the costume (I forgot about )

okeyy.....  start:

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2. Start talking to the NPC

hi >  wyspie >zostanę > strój > pokemon

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3. After leaving, go to the place marked on the map

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3.1 Open the hole and go down and left and then go up you will see the box containing "Luffy's Feet" 

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hi > tak > pomoc >miewa >przedmiot  

run out and come back

hi > zadaniem  

 You will get the rest of the mission

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back to luffy
5. Hi > część 

run out and back luffy , say 'hi" again 
tak > tak