Probably you have spoken about it earlier (sorry if so), but how do you think that Taigen will know Mizu's gender in the series? And how would you like it to happen? I would like it to be intentional, but regarding the amount of wounds Mizu constantly have, who knows...
Hello! :D And no I don't think I've ever written about it publicly on this blog, and to be honest I've never thought much about it.
To preface, I've not always been the type to properly sit down and theorise about future narrative decisions. When it comes to these things, I'm very "big picture" oriented, where I'd usually be fine with anything happening in the story as long as it touches on certain themes, remains in character, and adds something meaningful to our protagonists' arcs.
For example the only reason I came up with the Mizu's mom theory was because knowing exactly who Mizu's mother is (whether she is white, or royalty, or anything else), could, depending on the different posible outcomes, drastically alter Mizu's sense of identity and how she perceives herself, as well as morph the core themes and message of the overall story.
On the other hand, when it comes to the particulars of the inevitable gender reveal, I'm not picky at all, and I'm open to all the possibilities of how it would play out. This is because the outcome to all of it remains the same (in which Taigen finds out Mizu's gender), with only the process to get there differing, and in that regard, the question is then mostly on personal preference on tropes and avoiding cliches, and speculating future plot beats that would allow the gender reveal to happen in the first place.
Like you said, it could happen by way of Taigen trying to stitch Mizu up while she's unconscious or at least half-conscious, which would thus likely involve a big battle happening prior. A similar instance that comes to mind is Mizu's face off with Chiaki and the Four Fangs; iirc it's the only time Mizu is unconscious and vulnerable in front of Taigen. I'm not counting the time after they both fell out from Shindo and Fowler's fortress, because in that case, they'd both been completely KO'd. So anyway yeah, to get back on track, post-Four Fangs battle, if Ringo was not a factor, Taigen would've likely been the one to bring Mizu to safety and patch her up. From the framing of the scene, and Taigen's expression upon noticing Mizu look so vulnerable (because at this point he'd still believed Mizu to be nigh invincible, as we see from his daydream of him battling a giant Onryo in Episode 2), it's almost like the show was teasing us with the possibility of a gender reveal right there and then. But then of course, Ringo comes in and puts a stop to that happening (and thank God for that, because neither Taigen nor Mizu, on a narrative level, are ready for such a reveal yet).
Other than a Taigen-patching-Mizu-up scenario though, and outside of Mizu confessing to the truth herself, another possibility is that Taigen deduces the truth on his own. And this an idea that Ioana (@saessenach) and I were discussing, assuming a scenario where Taigen did not follow Mizu on the boat to London, but remains in Japan to do his own thing. In this scenario, all four of our protagonists are separated throughout Season 2 to have their own arcs: Mizu in London, Akemi in Edo, Ringo in Eiji's forge, and Taigen? Well, absolutely zero hints were given on where Taigen's going to go after S1, so everything's up in the air. The reason for this could be just some network/authorial reason whereby the writers are leaving it open because they themselves aren't sure what to do with Taigen.
Or, if they'd pre-planned everything early on, the complete lack of Taigen's presence at the end of the finale could itself be an indicator of where Taigen, and his arc, are going. What I mean is, Taigen in Season 2 might be a Wanderer, also known as a Ronin. Remember, he was disgraced and cast aside by his Lord, has lost his station and place in his Dojo, and him witnessing the "humiliating" death of the Shogun could be reason for Lady Itoh to want Taigen gone. He has nowhere to go. Plus, with him beginning on a journey of unlearning his prejudice and confronting his wrongdoings so he can properly change for the better (with the scene of him in Kohama in Ep7 being only his first steps), it's possible that his arc next season will be something along the lines of Zuko's from Zuko Alone in A:TLA. If you haven't watched A:TLA, what I'm referring to basically involves going from village to village, seeing that the status quo and society is cruel and unjust, trying to help people but having it kinda blow up in your face because of the fucked up status quo, and also facing the past you've been running from your whole life (through the form of flashbacks and introspection).
Thus, should a Taigen Alone arc really happen, it's possible that Taigen also gets wrapped up in some plot involving the black market dealers in these towns he visits, which would help tie in to the main story happening with Mizu and Akemi, because the white men (on Mizu's end) and the corrupt officials in the palace (on Akemi's end) both have ties to such black market dealers that Taigen may encounter. So it's possible that while investigating these people and tracking them down, Taigen gets wind of some rumours about the huge bounty on a half-breed blue-eyed girl. And, well, you can guess where it goes from there. Taigen deduces the truth, and when he reunites with Mizu later on, there'd be all this tension because now he knows. And this would be a very interesting outcome because this scenario wouldn't lend itself to a huge heat-of-the-moment argument that everyone's expecting, whereby Taigen finds out the truth while Mizu's right in front of him. Instead, in this case, Taigen finds out on his own, gets time to stew in the revelation, and likely drive himself mad in the process, and BOY THAT'D BE JUICY AS ALL HELL!
So basically, yeah, between the two scenarios I just presented, I'd favour the latter more, but I wouldn't mind the former either, or anything else the writers might throw our way.
However, I do still kind of hope Mizu could be the one to reveal the truth to Taigen herself, as I feel she should be allowed the choice in the matter, rather than having Taigen find out against her will. Plus, being the one to tell him herself would be such a huge step for her, signifying how she's opening up to people again, and would also be a big sign of some pre-established trust in their relationship.
BUT like I said, I'm not all too picky, and I also live for the drama, so, in conclusion: ¯\_(ツ)_/¯
Also I just realised just how much I typed up, and I'm so sorry that I can never be concise with my words, but I hope it's still somewhat legible. 😭 Thank you so much for this question by the way! I love rambling about this show, and I'm grateful for any chance to ramble about it even more <3 <3