This guy is met in many areas of the game. These areas include:

* Sitting beneath an umbrella in the central area beach
* Right at the entrance of the Biano Hills level


He won't give you anything until you get 30 shines. Once you have 30 shines, you can go to him at any time to ask for sunglasses. He'll give them to you, and your world will become darker. This helps when it gets way too bright to be able to see, once you have so many shines freed. You can always go back to him and give them back, if you like your world very sunny.

You also get a special shirt once you take care of the final boss!

Super Mario Sunshine Walkthrough