I finished up your oneshot! I didn't add in the little portion of your request, just because I didn't want to misrepresent anything or wind up being offensive or something. I felt most comfortable leaving that part out, so I just did trans Keigo at the start of his period.
I also don't quite feel comfortable posting this request because again, I really don't want to misrepresent anything, but I have written it and would be happy to share it with you. I could send it to you via email or discord or some other way if you'd like! Lmk.