Room Key

The Room Key is an item which is received in the Reuniting Kafei and Anju sidequest in Majora's Mask. Obtaining the Room Key is not necessary to reunite the two lovers, however, and the quest can easily be completed without it. This key allows Link to go in and out of the Stock Pot Inn before and after the inn closes without having to resort to using the unlocked door on the deck of the second floor. More importantly, however, it grants him access to the Knife Chamber, one of the two rooms available for rent on the second floor at the Stock Pot Inn.

Link receives the Room Key as a mistake due to Anju's tendency to forget customer's faces. When Link talks to her between 1:50 PM and 4:00 PM during the First Day, Anju will ask him if he has made a reservation. If Link says yes, she will hand him the key to the Knife Chamber. The reservation was actually for a Goron who just happened to have the same name as the young hero: Link. Since Link has the room key, Link (the goron) will not be able to claim his reservation and will now have to sleep outside.

Trivia
-The Room Key will automatically disappear from Link's inventory on the Final Day. At that point, the Stock Pot Inn is left unlocked for the rest of the cycle because all the employees have evacuated.