Jewel
is a very minor character in the Dragon Ball world. He makes an appearance in the Tenkaichibudokai and seems to be stronger then most humans but doesn't stand a chance against the Z team heros.
This cache is actually a lot more significant then the character in Dragon Ball. The name of this Charater just happens to be the name of a nearby cache called "Jewel of Okinawa" Here is a view of the cache location from "Jewel of Okinawa":
Getting to the top of that peak is a lot easier than it looks. To get there you need to leave the main path on the way to "Jewel of Okinawa" onto a smaller path that takes you to the top of that peak and the cache. That smaller path was not as well beaten as the main path so depending on the time of the year you may have overgrowth obstacles. And finding the smaller path may be the biggest challenge for this cache. The trail head is near a spot on the main path that offers a great view.
Once you find Jewel, you can get some infomation that will help a fulfill a wish.
Good Luck and enjoy the hike.