Akiko Yosano, a short-haired woman at the Armed Detective Agency. She is warm and friendly toward Ringo, preferring to be called big sister. She observes Ringo thoughtfully and questions whether Ringo has truly gotten over Dazai. She is perceptive and caring, wanting to pat Ringo on the head but restraining herself due to Ringo's shy nature. She asks Ranpo about telling Ringo what happened on Halloween.
