Law and luffy were neighbors and law really enjoyed to bully him. The scene of Luffy get angry or even hurt and shivering or crying was really making him happy and he didn't know why. He just tried to hurt luffy's feeling in every way he could.

One day Law was walking to him house but he saw luffy in the Middle of way. He smirked and then aporechaed him from behind and grabbed the top of Luffy's hair and pushed his back to the wall and leaned down toward him. "Whoa whoa...look who is here...hehe... Luffy-kun..."