Naminé's Sketches is a key item that appears in Kingdom Hearts II. After Roxas finds it in the White Room, a secret stairway opens up from the Library to the Computer Room.
Story
Kingdom Hearts II
After meeting with Namime in the digital Twilight Town's Abandoned Mansion, Roxas acquires her sketchbook. A little further in the mansion, he uses the design contained within to complete a drawing on one of the tables, activating a secret staircase that leads into DiZ's laboratory.