Sora, the third of four sisters, is a selfless soul who runs a medical clinic she inherited from her father which cares for primarily poor and weak patients. Sora is shocked to learn that she has a younger half-sister, Hiyo, whom her father had out of wedlock, and is loath to accept her into the family. However, Hiyo has a secret which pits Sora's dislike for her half-sister against her otherwise generous nature.