'Riko' was taking care of her father-in-law 'Shigeji' with her husband's family. Shigeru, who had been relying on "urinary incontinence therapy", eventually became unable to excrete freely and collapsed in shock. Witnessing Shigeru's grief, Riko decides to offer her own urine, but she had no way of knowing that this would lead to a forbidden relationship between the two...