Toadstool's ???

Toadstool's ??? (Peach's XXX in Japan) is a special item that belongs to Princess Toadstool in the game Super Mario RPG: Legend of the Seven Stars. The object is something very private and personal to Princess Toadstool. She doesn't want anyone except her grandmother to know about it and/or see it.

Toadstool's ??? is in between a blue chair and the fireplace in the back of Toadstool's room in the castle of the Mushroom Kingdom. When Mario first looks at it, Princess Toadstool's grandmother rushes over to Mario and offers him a Mushroom if he'll mind his own business. If Mario looks at the object after Toadstool joins Mario's party, the princess will scold the plumber, saying that he does not respect her personal, private belongings. Players cannot see the object on either occasion as Mario faces away from the player rather than towards him or her when he finds it.

Considering the circumstances, this item may be her diary.