As a teenager, she was caught breaking into the lab of Dr. Mann's father, who then arranged for her to receive training in the martial arts from The Perfect Circle, an organization formed in the 1940s by Emperor Hirohito as a countermeasure to the Culper Ring. In the "Motherland" arc, she reveals that one of the reasons she stays in Dr. M/Dr. Matsumori's employment is so she would be given a long line of clones, thus "(she) would never really die."
This passage describes a character's motivations for working with Dr. Matsumori, highlighting her desire to achieve immortality through the creation of clones.