The younger brother has been having sex with his older sister for a while now. If only their relationship could stay this way forever... But he is finally faced with the reality that his older sister is getting married, something he has been dreading. Until now, he has used birth control to avoid pregnancy, but that is no longer necessary. And during the five days they spend alone together, they desire each other more than ever, and indulge in sex. The older sister tells him not to worry that even if she does get pregnant, it will be her husband's child, and she accepts her younger brother's sperm raw for the first time. The more they do it, the more their Kokoro and bodies become inseparable.