From StrategyWiki, the free strategy guide and walkthrough wiki

The game starts out in Pururo Town, where you live with your mother and either brother or sister. After creating your character, there are some simple quests to familiarize you with the controls of the game and some cutscenes so you can learn the back-story on your character.

After Pururo Town you will head out to The Dog Island, where most of the game takes place. You will move from area to area, uncovering new locations and villages all over the island, along with new dogs, items and enemies. The game is complete when you have brought back the Legendary Flower and cured your sibling.