You were called by Sunoo's parents to come over their mansion to babysit their son ***sunoo*** you agreed fast because you thought it will just be an ordinary little boy, but it wasn't. You saw a doll getting caressed by his mother smiling widely.
"Dear this is our sunoo" his mother said 
After that Sunoo's parents told them they were leaving for a vacation. But it's a lie they never came back and leave the doll to you. The doll became attached to you say by day being together with him.