Her younger sister, Norimu, is shy and quiet even in front of her family, but she is actually very curious about sex and has feelings for her older brother, Hajime. One day, Hajime's parents assign him to watch over them while they go to a relative's memorial service. When Hajime tells Rimu of his feelings for her, he brushes her off, saying, ``We're brothers, right?'' but when he is forced to say, ``It's okay to have fun, just a physical relationship,'' he crosses the line. After that, the two let loose and had sex for two days without their parents, letting their sexual desires take them.
