To complete the Rainbow Paradise quest, you need to find hidden boxes that are scattered around locations in hard-to-reach places.

Boxes appear in different places, but not far from each other.

Rainbow Paradise in Hope 101

The first box is on the market itself, you need to climb the boxes, at the beginning of the market or at the end.

A second box can be found on the roof of the main building.

The third box is in this store

You will find the fourth drawer in the first building, on a closet by the landing or in a room on the 3rd floor.