I enjoy what you're doing with the portraits! It's nice to see your style developing, and the various music remixes are fun. On top of that, the use of actual historical references is extremely impressive and gives a good realistic aspect to the story.
The premise of introducing a newcomer to Gensokyo is especially interesting in a trans girl context, although I did notice the writing feeling unsteady. Tsuyu seems highly surprised if not shocked at her new look & role, but didn't grapple with it as tensely as I would have expected of somebody with an entire former life. (The sudden long hair also almost threw me off for similar reasons, especially being unsure when/if timeskips were happening.) Likewise, I was particularly surprised by how fast she gets shipped with other characters, especially ones just introduced.
I would be very interested in seeing Tsuyu's internal (and external) conflicts explored more, especially her self-discovery. In our world, I find that a lot of people can have hidden internal conflicts and thoughts on their situation that all lead up to how they view & express themselves - and how they interact with others. In storytelling, having purpose to those kinds of events would add a lot of impact to them.
Aside from that, the writing feels alive, and I enjoyed the lighthearted read. Well done!