Small Master Key is an item in White Day: A Labyrinth Named School (Remake).
If you acquire it, you can find the document & Some Old Figures.
It is found in a box of the Student Department Office wall, 2nd floor of the Main Building, Section 2.
To open the box, you need for a password and it can be found in a document called 'Dying Message'.
If you collect all Typewriter Buttons and put into the typewriter at Faculty Office 2, you can get a document called Dying Message
( But, It is possible When you play the Normal mode or more )
It is used to acquire the School Ghost Stories (1).
And if you play in Wang real [King real] Mode, it is possible to acquire the some old figures by using this key.