First go to Rustboro city. then go to the house above the cutters house. after you have done this go up the stairs and you should see a man standing next to a bed in the bed is a girl. tlk to the man and he will ask you for a pharse to make his daughter smile. guess it right and he will give you something.

P.S-i dont know what it is,so if you find out plz post it on this website.