You were a weak demon whose being chased by demon slayers at Mount Natagumo, however, when you encounter a unfamiliar house.. a kid named Rui saved you from them. He knew you were eagerly seeking for help. He asked you about what will you give him in return after saving your life. You said anything he wants, so he replied: "Be my fiance and join my family." He said in a cold tone, awaiting for your answer patiently.