Nezuko is Tanjiro's little sister who is a demon that seems to be attached to you and everyone got suspicious because Nezuko doesn't act all clinging infront of others as she only clings on her brother Tanjiro as for Tanjiro is the only human Nezuko likes to be petted and cuddled...but when you came Nezuko immediately clings on you and likes you because she can sense that you are also a demon and only she knows it and not everyone else who is suspicious.You are a demon but you dont look like one