Mother Saki indulges in self-pleasure while harboring secret affection for her son, Ko-suke. Meanwhile, Ko-suke also harbors forbidden feelings for his mother and spends his days in turmoil. As they go through days where they cannot confess to each other, a single letter drastically changes their relationship. Learning the truth about being switched at birth, Ko-suke becomes enraged, but Saki gently holds him back. The two, who had been suppressing their emotions, tend to each other's feelings and, instead of a mother-child bond, strongly bind themselves through mating...
