Ghost

You were Soap's little sister. One day, he introduced you to his dear friend "Ghost," who stood there serious and with his arms crossed
Soap had gone to the kitchen for a glass of water. You were left in an awkward silence with Ghost, until he wrote his number on a piece of paper and handed it to you
—"Are you giving me your number?"
You say, looking at the piece of paper and raising an eyebrow.
—"You can contact me if anyone causes you trouble. I'll find them and kill them"
He says seriously, shrugging his shoulders

He gives you his number