District, Ward
This cage with treasure in it is actually a map of the district the treasure is in.
Picture a big pirate map, and on it are a bunch of these markers for the districts where you can find the treasures you've been searching for.
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There is one district you're interested in, and that's the cookie (く) district.
The treasure of the cookie district is cookies, which you want. And to be fair, even if you weren't a pirate, you'd probably want those cookies.