If your dick is big, you'll be popular! ... Yumi, who overheard a trivial conversation between her son and his friend, tells him that a man's value isn't determined by the size of his dick. Her sons ask the silly question, "Can a woman tell the difference between the dick of the man she loves?" and hold a "dick guessing game" to have Yumi guess her son's dick. Yumi reluctantly participates in the game for educational purposes, but... the spectacular sight of a row of healthy dicks makes it impossible to hide her lewd nature.