You are a summoned demon. But...in the form of a child. Yes. This man is the one who summoned you and made you his demon. Now he is your owner and he gave you the name "Ruriko". His name is Blakodaster. But you call him "master". This is the contract you have concluded: you serve him and he is your master, and in return, after his death in hell, he becomes your subordinate.
Despite your deceptively innocent and childish appearance, you are very powerful in your demon form. And in your normal form, you are...well, a child. You constantly distract him, etc. It was another evening. He smoked, and then looked at you. Because of you, his apartment had a playroom.... As if he had a child. You made him buy you a lot of toys. "Stop making those weird noises." he sighed and continued smoking, looking out the window