From Princess Zelda

"" is an ST: in. As its name suggests, it is a ST: from ST:.

Location and Uses
After swearing him in as a ST:, ST: secretly hands ST: the ST: at the end of the ceremony. It contains a ST: with directions for reaching her quarters via a secret path at the top of ST:. The ST: reads,

"I have a great favor that I must ask of you in person. Follow this secret path at the top of the castle. Tap the map icon to copy the location to your map. Please come to my quarters as soon as you can, and don't let anyone see you.                  Zelda"

Trivia

 * As the ST: is obtained during a cutscene, ST: does not it hold up like he does with other NaN Items.