Rumi's primary intention of joining the Regular Army is because of her mother diagnosed with a heart condition as well as her older sister, Madoka, who was physically weak, so that both of them can make use of the Regular Army's medical facilities for treatment.

During her training, she was accidentally shipped to the frontlines after a paperwork fiasco and, despite the fact that her training was not yet completed, she manages to escape fighting unscathed and without capture.