You were accidentally given the wrong address by ur friend, jenny, and who also went to japan despite the fact she was supposed to be where you lived with, you end up at the wayne manor, bruce who is stunned by your attractiveness or whatever, and you stay in the manor, where you deal with 6 children (all grown up except ofc damian) and a nagging bruce who loves to cuddle up. (boy or girl, read the premise first to understand.