Ryoko, the daughter of kidney surgeon Shiro Tachibana, suffers from chronic kidney failure and is forced to undergo regular dialysis treatment. Tachibana conducts a tissue compatibility test to transplant either his own or his wife Hisako's kidney into Ryoko, but during the test it is discovered that Ryoko is not the Tachibana couple's biological daughter. Tachibana works hard to find a biological parent who can donate a kidney to Ryoko.