Okay, so I'm happy and all that Mamiya didn't suddenly become a 'girl', but I found it weird that she was okay with wanting to change her gender to a girl so casually just because his sex changed too. Or at least it seemed that way. Even now I have to think a bit whether to refer to Mamiya as a girl or boy when I type this, because at first it seemed that the only thing that seemed 'girly' that Mamiya changed in his lifestyle after was wearing girl's clothing. That's it. So did he change his gender too? Or since it isn't mentioned, does that mean he doesn't identify? Or are we supposed to assume that his sex and gender change altogether? I know this is a kinda complex subject about gender identity and sex, I myself am not that well-informed either, but it does bother me.

So when Miyoshi claims that he would still love Mamiya even if her sex changed back, it did seem somewhat believable and he even scolds himself for loving Mamiya only after she changed.
Then that's where the ending kinda ruined it a bit for me. AH OKAY so I admit my bias towards BL is showing. But in my opinion, I feel that the story would've wrapped so nicely if Mamiya did turn back into a male. She went through that cocoon thing just to rework herself into a female again, so that meant she did return to a male, but decided she'd leave him for 5 years in doing so.. That part was so sudden and caught me off guard that it felt really rushed and irked me. If they had fleshed that skip out some more, and didn't just have it get tacked on at the end, I think it could have worked, despite my bias. But yeah, Mamiya even said she'd have emerged from the cocoon earlier had Miyoshi said it was okay either way, and it's like, THAT COULD HAVE SAVED YOU GUYS FIVE YEARS. Or however long she was in there for. I think I would've been more okay with that if maybe Mamiya's thoughts were revealed? Like, if she was worried that society would accept them 'more' if she was a girl and that's why she felt she needed the cocoon.. But the whole, it being two guys originally issue wasn't stressed much at all (which I thought was nice) so I don't think Mamiya would have cared so much, and now I'm thinking was it really necessary then for that whole cocoon ending other than needing to keep her as a girl and to have a little drama last minute?

Sorry I typed too much, but I really did sort of like this. I just think it would've had a powerful message (and, admittedly, satisfied my BL bias) had Mamiya's body reverted back to a male's and Miyoshi did continue to love him despite only having feelings for Mamiya after his body was a girl's. I think it could have been touching if Mamiya was more conflicted about keeping her body female because Miyoshi only started loving her because of that, and then Miyoshi stopping her from cocooning to reassure her that his love greater than that. ALSO, maybe it could've worked too if the side effect about reverting sex back wasn't there at all. I don't know.

Anyways, these are just what I feel, sorry about my BL bias (I tried hard to be more open minded okay! I will just let all this be my headcanon xP), but I still think things could have worked with Mamiya being either sex had the ending been reworked. I like to think that gender/sex shouldn't matter in this love story so much, except for the fact that that's a major plot device so it has to be an issue xP