Osome, who works as a dance and shamisen instructor in Ryogoku, is a former entertainer who lost her parents in a fire at age six and was separated from her older brother during the tragedy. Known as "Yozakura Osome" for her beauty and artistic talents, she once served as the star performer of a theatrical troupe. When Osome asks Sasahara Yahei, a doshin officer at the South Magistrate's Office, to investigate the fire that claimed her parents' lives, she eventually learns from Yoshikawa Tateaki that her father had been a government spy working for the shogunate.
Upon discovering this shocking truth about her father's secret identity, Osome becomes determined to capture the perpetrator responsible for her father's death and to search for her missing brother. This revelation transforms her understanding of her family's past and sets her on a dangerous path toward becoming a covert operative herself. Under Tateaki's guidance and training, Osome resolves to enter the shadowy world of espionage, using her skills as an entertainer as cover for her true mission of seeking justice and family reunion.
