@miyako19
Go read the author's notes on the Uesugi Kenshin succession problems and Tokugawa Outright banning Female lords etc.
https://mangadex.org/chapter/672913/9
https://mangadex.org/chapter/672913/10
The Useugi Kenshin is a Women theory is essentially rumor anyways, all circumstantial evidence and no concrete evidence. Given the context the author explains, it was a plausible theory with no concrete proof possible. The author covers it.
https://mangadex.org/chapter/672913/6
https://mangadex.org/chapter/672913/7
You got me on the clan head thing. I honestly don't know enough about the nitty gritty to argue the details on that.
As for the Tokugawa banning female lords thing and trying to remove women from positions of power, that was a real thing. It was a movement called neo-confucianism introduced in the Edo (Tokugawa) period to systematically remove women from positions of power and reinforce Confucian gender role ideas. Remember how women were banned from Kabuki? Yes, that was partially due to Neo Confucianism as well.
That trope where female Samurai ladies always had Male bodyguard escorts? Require by law under the Tokugawa, the less romantic part was they had to have special travel permits to go through checkpoints and many of these Sekisho checkpoints blocked access and restricted Women from going through them. Local women could be allowed through certain gates, but many of these checkpoints simply blocked all women from going through them.
This was so bad, there were things called "Women's roads" that women HAD to take. Pretty dumb when you think about it, but the Tokugawa were all about castes, controlling people and enforcing social classes that you couldn't move between.
https://wiki.samurai-archives.com/index.php?title=Sekisho
https://en.wikipedia.org/wiki/Edo_neo-Confucianism
https://en.wikipedia.org/wiki/Onna-bugeisha#Sengoku_Period
In fact, this Neo-Confucianism thing is prevalent in modern Japan to this very day, with massive repercussions.