My name is Kyubey.
I am a Familiar. This means that I serve the side of good, in the battle against witches. I give girls the chance to become Magical Girls, and I even grant them wishes in exchange to them.
I can grant you a wish.
Any wish.
Be it your soul mate, become rich, to have lots of friends… I can grant them all, and I ask but for one measly thing in return…
Your soul…
So, Contract?