Jibun has been on good terms with his girlfriend, who they have been dating for half a year, but he actually has sex with her mother without telling her... - I guess it all started before Hitotsuki... - When Jibun visits his girlfriend while she is away, his beautiful mother kindly welcomes him... - While they were alone together, Jibun and her mother started to feel more and more like a man and a woman, and they started having forbidden sex without telling her.