Right of the bat, this kind of situation did happen in history. In fact, there are so many similarities that I'm convinced that Samura, the mangaka, was directly influenced by it(more on this later). The event I am referring to is the second Sino-Japanese war. Specifically the comfort women in the war. I am not going to go over any details about the war itself since I am not qualified enough for it and you can Google it at your leisure but I will specify what "comfort women" are.
If you are an eastern Asian, then you probably already know what those words mean, but it is very rare that a westerner knows them. During WWII, the Japanese military would trick young Japanese girls, often underage, into joining the military and turning them into sex slaves. They would lie to the girls about how they can become nurses or medics on the front line. Telling them that if they join the army, they are serving their empire and making the emperor proud. After they run out of domestic girls, they start to kidnap girls from China and Korea.
As I said, there are a lot of resemblances between the manga and the real-world event. The manga promises the girls in the orphanage a better future in the theatre. While the military manipulates girls with patriotism and a promising career. The manga states the carnival has been going on for 7 years, while the war lasted for 8 years. The cabinet abolished the carnival after learning they could be exposed, while the military executed most of the comfort women after Japan lost the war to silence them. A very interesting point is that the noble who started the carnival was killed by a plane piloted by two men crashing into his castle, while Japan lost after being hit with two atomic bombs, named fat man and little boy.
What I have provided is just one example, but not the only one. There are tons of instances in history where young, innocent girls are traded as sex workers, either for money or supposedly stability (watch Sandakan No.8 for more details). Orphanage forcing its kids to work under harmful conditions is nothing new.
The final question then becomes why? Why did Samura create a manga with such cruelty and depressiveness inspired by real-world historical events? This has to do with how he writes and draws women in general. Samura believes women are superior to men, and in his work, women are always mentally or physically better. Makie is the strongest character in the blade of the immortal with most female characters being either very courageous or strong-willed. This all might sound conflicting considering the ill-fated girls in the manga, but that is kind of the point. Just like how the festival is abolished in the end, the treatment for women is getting better as time goes on. But we must not forget the poor treatment of them in the past. Or he is just a huge hentai who gets a kick out of seeing women suffer.
