During the Russo-Japanese war in the 37th year of the Meiji Era (1904), a small Japanese army sought assistance from their special flying ship, the Amanohara. With the help of a benevolent demon, they used this ship to attack Russia's major base at Lushun, also known as Port Arthur. Meanwhile, Umakai Shintaro, a Russian diplomat originally from Japan, defected and traveled to Sapporo to teach at a rather unconventional girls academy. The Raimu Unit, a group of five girls with the power to summon formidable creatures to fight alongside them, made up the student body of this school, which was hosted onboard the Amanohara itself. Shintaro soon became their mentor and leader in battle. As they prepared for their final stand at Lushun, he helped the girls to overcome their weaknesses and strengthen their abilities. Nevertheless, their journey was not without its peculiarities, including its excessive eroticism. Meanwhile, they also struggled to understand the motives of the "Russian Spiritual Corps", who had joined forces with their enemy. To make matters more complicated, one of the members of that Corps was someone Shintaro knew all too well...