That is only 1 example, out of a couple thousand years in history in Japan.
And another fun note, the wikipedia article to Uchida, only contains 1 source, which is, https://kotobank.jp/word/%E5%86%85%E7%94%B0%E5%AE%B6%E5%90%89-1057909. It never even mentions how he died, only who he served, which clan he is from, and his legacy.
The source itself, mentions no historian, no references from historical written, so I find it really hard to believe that he died to a slash from a katana, when polearms, muskets and bows dominated the Sengoku battlefields, much less the existence of an Uchida Ieyoshi in the first place.
In response to OP, there won't be women in your standard recruitment form armies, but you may see companions, leaders, and important NPCs who are female, and it should stay that way, to represent the rare role women played on a medieval battlefield. You can still choose to play as a female.