So the transformation seems to be based on whether Noel and Eito want Keisuke to be a girl or not, but it's kinda unclear whether Keisuke is included in that, too. Like, is it just about consensus between those two, or would Keisuke and Noel both wanting him to be a girl cause him to transform, even if Eito wanted him to be a guy?
Going back to the first switch-back in this arc, when Keisuke and Noel are trying on swimsuits, it's not entirely clear if it was triggered by this consensus mechanic. I'd say it probably isn't, because it seems unlikely that either Noel or Keisuke would want him to be a guy again there, considering the awkwardness of the situation.
But the switch back into a girl afterwards, though, might be, if we Keisuke counts as one of the voters, because at that moment he was dramatically panicking about what would happen when Noel saw him or he left the changing room. Thus the change could be triggered by him and Noel beating out Eito 2-1.
This would assume that Eito wanted Keisuke to be a guy again, though, so maybe the original change was a consensus between him and Keisuke just generally wanting to be a guy again? But I can't remember there really being any indication of Eito wanting that, and I'm not sure what would have triggered that in the first place.
While at the beach, he mentions the thing about how Keisuke won't fall in love with him if his heart is a man's, which would suggest that at that moment, he wanted Keisuke to be a girl, (The same way he wanted him to be in this chapter, triggering the switch back to a girl here.) and it kinda seems like that's something that he's been thinking, not something new he just came up with.
Which would suggest that at the time of the switch he wanted Keisuke to be a girl, not a guy, and so the theory that that switch was caused by consensus breaks down unless we somehow come up with a reason for Noel to want Keisuke to be a guy at that moment, which seems unlikely considering the circumstances. So at that point, that's a 2 in favor of him being a girl, and so he shouldn't have switched, regardless of whether Keisuke's been included in the vote.
Plus, with the switch back there, he was panicking for a while before switching back, while the switch back to a guy at the beach seemed basically instant, as far as we can tell. As soon as the last of them decided they wanted him to be a guy, he was one.
And that all makes me think that the situation is a bit more complicated than just a Eito–Noel or Eito–Noel–Keisuke vote, so it's hard to say much of anything about the specifics of the mechanics right now, beyond just "if they want it, he switches." I wonder if there're other people included in the vote?
Because this might all makes more sense if there're five people: Eito, Noel, Keisuke, and two others. Like so:
Changing Room Switch 1: (FtM)
GIRL: Eito, Noel; (2) BOY: Keisuke, №4, No. №5 (3)
-> One of the additional voters suddenly decides they want Keisuke to be a boy, and thus boy wins. (Alternatively, maybe the voting system was introduced here, and this just happened to be the position everyone was in.)
Changing Room Switch 2: (MtF)
GIRL: Eito, Noel, Keisuke; (3) BOY: №4, No. №5 (2)
-> Keisuke panics and wants to be a girl, and thus girl wins. Of course, №4 and / or №5 could also have decided to want Keisuke to be a girl again here.
Beach Switch: (FtM)
GIRL: (0) BOY: Eito, Noel, Keisuke, №4, No. №5 (5)
-> Everyone who had wanted Keisuke to be a girl before want him to be a boy suddenly for various reasons. Boy wins.
Hotel Switch: (MtF)
GIRL: Eito, Noel, №4; (3) BOY: Keisuke, No. №5 (2)
-> After thinking on things a bit, Eito and Noel both return to wanting Keisuke to be a girl. One of the other voters makes the same decision for whatever reason. Girl wins. Both additional voters could be on the same side here without changing the outcome.
Alternatively, Keisuke could just get two votes, with only one additional voter, as pairing him up with one or the other doesn't change any of the outcomes. You can even already see that he's on the same side as "№5" in every event in the list I just made, with the exception of CRS2, where switching №5 doesn't change the outcome anyways.
№4 and №5 could be paired up as well without much issue. The only problem is that they'd have to change their vote for HS, as while they safely stay on the boy-side for the first three, for HS if they vote boy, then boy wins unless we can find some excuse for Keisuke to want to be a girl then, which seems unlikely while seeing how he acts here.
Either way, the question is who else could be included in this vote. If I had to guess, I might say that Tobii is the extra voter, with either her or Keisuke being worth two. Because, like, what other options are there? The only other major enough character would be Noemu, but she clearly wants Keisuke to stay a guy, which makes HS impossible unless she, Eito, or Noel is a double-voter, and there's not much justification for any of them being it.
Without the double voter theory, of course, the two extra voters could be Tobii and Noemu, with Noemu being "№5," who wanted Keisuke to be a guy all along, and Tobii being the one who suddenly switched in HS and possibly CRS1. (Though I think that the new rules being implemented here seems more likely.) But this has the issue of there being no real reason for Noemu to be included in the vote, especially with how she was introduced this very arc.
So Tobii being extra voter with either her or Keisuke being the double-voter seems like the best option right now, and I think that there is a pretty good justification for the theoretical changes in vote she'd have had. At first, she might have introduced the vote system so that she felt guilty about not being able to take back Keisuke's wish, using the vote as a way of getting around that, so she'd want him to be a guy then because that's what Keisuke wanted. Then, the system was put into place, causing him to suddenly turn into a guy in the changing room. She was not watching Keisuke at this time, and so Keisuke's the one to trigger the change back, utilizing the new system.
We know that Keisuke went back to her shrine after this, so after hearing what happened, she decided to switch her vote to him being a girl, so that he wouldn't have to worry about a surprise switch while at the beach. (It's unclear where she heard about this specifically, though, as he didn't actually say anything while at the shrine. Maybe she followed him to Eito's house?) She's now no longer observing again, so her vote stays that way until the present moment. This would make the revised version of the list above as follows. (Assuming that Keisuke is the double-voter, as it seems fair for him to have a larger say, though Tobii being like "I'm a god, I get two" is totally possible as well.)
Changing Room Switch 1: (FtM)
GIRL: Eito, Noel; (2) BOY: Keisuke, Tobii (2+1)
-> Tobii wants Keisuke to be a boy because he asked her to turn him back. Keisuke just generally wants to be a guy again. System is introduced, so the current states immediately trigger a change. Boy wins.
Changing Room Switch 2: (MtF)
GIRL: Eito, Noel, Keisuke; (3+1) BOY: Tobii (1)
-> Tobii is not observing and so doesn't change her vote. Keisuke panics and wants to become a girl again. Girl wins. (No explanation for the delayed switch. Maybe he just wasn't panicking hard enough until she went to open the curtain?)
Beach Switch: (FtM)
GIRL: Tobii (1) BOY: Eito, Noel, Keisuke (3+1)
-> Tobii wants Keisuke to stay a girl while at the beach so as to avoid any unfortunate accidents after finding out what happened in the changing room,. Eito, Noel, and Keisuke all think things through and decide they no longer want him to be a girl. Boy wins.
Hotel Switch: (MtF)
GIRL: Eito, Noel, Tobii; (3) BOY: Keisuke (1+1)
-> Tobii is not observing and doesn't change her vote. Eito and Noel think on things and decide that they actually would like Keisuke to stay a girl. Girl wins.
Of course, if this is the case, you kinda have to wonder why she stopped showing herself. Maybe introducing the current system is taking up more energy and making it difficult for her to materialize properly? Like, she sleeping at the shrine or something, and had to be "woken up" by Keisuke going there for her to go and investigate what happened, after which she fell asleep again. There's not really any evidence for that, but it is one possible solution.
Also, crack-theory, no one has a double vote and we, the readers, are the fifth voter. At CRS1 we want Keisuke to be a guy because it'd be funny, tipping the scales. At the rest, our vote doesn't matter. This is definitely right, because it was pretty funny, you gotta admit.
Seriously, though, the fifth vote only really matters at CRS1. If we have Tobii as the fourth, then everything works out everywhere else, and even CRS1 would just be a tie. Maybe Keisuke just acts as a tie breaker or something? Or maybe "boy" just always wins the tie by virtue of it being his original form? Though, personally, I kinda feel like a tie should result in "stay whatever he already is," myself.
Anyways, apparently this comment is 1,696 words long.