According to Japanese folklore. A spirit of a little girl haunts the third bathroom stall, waiting for someone to say her knock on the door so she can 'play' with them. 

 

If you go into the girl's bathroom on the third floor, and walk to the third stall, you might find it. You have to know on the door three times and call the girl's name. The light's start to flicker and a bloody hand print appears on the door. 

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The hand print belongs to a little girl known as Hanako-chan. She wants to find a friend to play with, maybe. Or she wants to drag you down to hell with her.