Sayoko has a very dark personality and is not very responsible. In the manga, she is suicidal, though this aspect of her character was cut out in the transition to the anime. Despite this change, however, she still remains irresponsible in both productions, but wants to make Asami happy and to live with her for a long time. Their room is filled with cardboard boxes, which they use as furniture and bedding, being extremely poor. Her father is a rich sculptor, with whom she became estranged from in her youth. Her favourite food is Mizuyōkan. Despite her evident uselessness throughout the series, she really cares for Asami. Though her age isn't revealed in the manga, her birthday is October 17.