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,'' but when Rimu is forced to say, ``It's okay to have fun, just a physical relationship,'' he crosses the line.