I can tell that you had a lot of fun doing the portraits! They're very expressive, including the Marisa wink one with the star effect. I also always appreciate being able to visualize the surrounding environment via things such as the sketched-in background.
The writing does a really good job of being varied, and the QTE dialogue style makes for an interesting gameplay element - trading off the ability to think through options for Marisa's on-the-spot scenario. I wonder if the timer could be adjusted or configured by the player somehow, depending on what the Ren'Py plugin allows. That may be a good way to accommodate different level of reading speed, including non-native levels.
Aside from that, I really enjoyed the storytelling and the depth of Marisa's & Reimu's interactions with the world around them. Combined with the creative use of limited colors, this was very well done!