Arakawa's first love is his friend's mother, Nanao, whom he has secretly admired since he was a child. Her beauty and large breasts have not faded even with age. Her kindness and concern for him makes his heart flutter. However, Nanao is his friend's mother. No matter how much he feels for her, his love will never come true. Just when he was about to give up on this fruitless love, he accidentally finds out Nanao's secret. Arakawa can't contain his excitement when he comes into contact with the lewd side of the woman he admires...