Zac to Ombra: Maboroshi no Yuuenchi

Every 50 years, an odd festival takes place on Delfino Island, and the main character, Zack, a magician came to the island to take part in the latest festival. However, a mysterious blob-like creature known as the Ombra has overrun the island and is causing trouble for the island residents. Zack happens to be one of the few people who can actually see the Ombra, and so it's up to him to restore smiles to the island's residents.