CONTAINS SPOILERS

To gain access to the metal cabinet in the secret room inside of Starry Eyes Bar, first read the note on the right side of the room. The clue is "Passcode: Date date!" Next, read the notes on the refrigerator. The passcode is revealed: "October 14 - Date with the princess!" Finally, go to the metal door next to the refrigerator and enter the passcode "1014" to obtain a special item.