A complex question, and one I can only answer with limited knowledge of the subject. As far as I understand, it goes something like this:
In the 1500s in Japan, it became increasingly common for noblewomen to be armed and trained in the use of arms to fight in the constant wars of the period. During the long period of peace in the 1600s and 1700s and 1800s, it became less common, but remained acceptable for women to be trained in the use of arms for ritual/recreational purposes, but no longer for warfare. This picture was taken in the 1870s, the Meiji period, just as/before Japan adopted 19th century European standards, so this was the 'last hurrah' of armed women in Japan.
After this, traditional weaponry declined as a whole, to the point of samurai turning in their swords to the government, and in the 1930s, when Japan decided they wanted to reintroduce traditional swordsmanship to army officers, they had to stamp out cheap swords on an industrial scale because so many had been lost or destroyed since the Meiji-period.