Tsuda Umeko-- featured on Japan's newest banknote-- is widely known in Japan as a pioneer of women's English education. Yet a remarkable chapter of her life remains largely unknown: during her second stay in the United States, she studied biology at Bryn Mawr College and was regarded as a promising young scientist. Drawing on letters and archival materials, this book reveals how Umeko immersed herself in the emerging world of biological research, why she ultimately stepped away from research, and what her choices suggest about gender, opportunity, and ambition in her time. By reframing Umeko not only as an educator but also as a woman shaped by scientific curiosity, this work offers a fresh and compelling perspective for readers interested in women's history and intertwined development of science and education.