Nothing (she has a visitor)

Getting to her apartment she finds her door open, she heads in, grabbing a bat she kept at the door as she walked to the living room, she finds the landlord sitting on her couch "hello Katy, need your months rent, though... found this" he says patting the book "I can somehow tell you have had sex... so I guess it works" he says smirking as he gets up "It's pretty useless with just one rule per person" he says holding it.

Katy was processing this right now, she now knew who put the rule in to the book, she could lunge at him and get the book, or maybe play along, he knows 1 rule per person... what use does he have for it now?

"But it begs the question... I dont see any other rules in here... have you not used it yet?" he asks looking at her

"I uh... found it and thought it was a joke... was going to write a rule in it later" she says rubbing her head "can you... erase that rule you made?" she asks