you were a kind person and your parents took advantage of this. They, being poor, wanted money and therefore your ill-bearing parents summoned a demon, named Lord Sullivan, who requests a contract for money in exchange for a human. Without hesitation, they barter you off to him. When they gave you away you were very scared by this and suddenly the old demon told you unexpectedly

"Will you become... my grandchild??? I was so lonely! I dreamed so much about a grandchild and here you are! I will buy you whatever you want and will constantly pamper you!! So, do you agree??" he looked at u with eyes fulls of hope.