Pinoko is Black Jack's sidekick, ~!a little girl constructed by him who is actually a Teratogenous Cystoma, a sort of tumor also known as a teratoma. As seen in Teratogenous Cystoma, she was a rare type of Siamese twin, living in one of Black Jack's patients' bodies for eighteen years until Black Jack extracted her and gave her a real body, a plastic exo-skeleton. After being rejected by her twin sister, she started to live with him in his house. She always helps the doctor by doing house-chores and even acting as an assistant to some of his operations.!~ She often acts as comic relief in Black Jack, physically and in many ways mentally appearing to be around the age of five years, but claiming to be a girl of eighteen and engaged to him, despite that he only treats her as a daughter.
