Nangoku Shounen Papuwa-kun

Papuwa-kun is a young boy living a quiet life with his dog, Chappy, on a small island located somewhere in South Pacific, when Shintaro, who is being pursued by gangsters, invades their happy existence.
Chappi takes Shintaro's precious Jewel, thereby making the two main characters lifelong rivals. Together they experience a series of bizarre adventures and situations.

(Source: AnimeNfo)