Super Mario Sunshine/Delfino Plaza

After the scene, go down to the Main Square. Defeat the Goo Monster like the one in the airstrip, but be careful because this one makes Goopys. Once it is defeated watch a scene(with all these scenes, you should bring popcorn). Now chase Shadow Mario while spraying him(the music will get louder or softer depending on how close you are). After you defeat him talk to Peach and follow her orders. Shadow Mario will escape into the graffiti. spray it until light comes out of it. Now, jump in. Now you are in Bianco Hills