Seiko spoils her useless younger brother who is a junior high school dropout who has never been able to get a steady job and just lounges around at home. He has been abandoned by his parents for a long time, has no ability to live on his own and has no girlfriend. His sister continues to be devoted to him and even takes care of his private parts, but she still continues to affirm him... All of this is for her brother's sake... What is the true purpose of her abnormal supportive love?