Sora, the third of four sisters, inherits from her father Sakamoto Medical Practice in Kabukicho, Shinjuku. Sora sees even those with no money and the waiting room is always crowded with penniless patients. Keeping the indebted surgery going is tough but Sora manages to carry on with a smile and becomes a popular figure in the neighborhood.

The oldest sister, Umi, is a single doctor researching gene therapy. The second sister, Riku, is the wife of the owner of a large hospital. The fourth sister, Mimi, is a trainee doctor dreaming of becoming famous. The four of them have very different stances on what it means to be a doctor, assuring that every gathering results in a fraternal fight.

One day, Umi calls the four sisters together and introduces them to a young girl they have never seen before. It turns out to be Hiyo their heretofore unknown half-sister from Hokkaido. Hiyo is very sick, her body being invaded by a heavy illness.

(Source: DramaWiki)

부모님은 돌아가시고 남은 3자매에 떨렁 남겨진 늦둥이 여동생. 그것도 정체는 아빠가 바람나서 밖에서 낳은 딸.... 그녀를 받아들이기 위한 여정...