Rio Mizushima is a character from the anime series "Black Jack," which follows the adventures of the unlicensed yet extraordinarily skilled surgeon, Black Jack. Rio is known for her cheerful demeanor and her role as a nurse who assists Black Jack in his various medical endeavors. Her compassionate nature and dedication to helping others make her an invaluable ally to Black Jack. Throughout the series, Rio provides emotional support and helps bridge the gap between Black Jack's often cold exterior and the patients' needs, highlighting the importance of empathy in healthcare.