An OC game submitted for a Touhou Jam... very bold move! Despite the focus on OCs you did ground the setting in the Touhou universe, which I think is nice and would fit in with the guidelines. I think there could have been more questions related to Touhou than just the SDM and Reimu one, however.
The trick round was an interesting concept and I wish it could have been explored more, but I guess it can be frustrating. I'm glad there are checkpoints at least.
Visuals and audio were definitely the highlight of the game, I think the style lends itself well to the tone and gameplay you were going for. I do hope you can create more works with this style if you want to, you can definitely stand out if you hone your skill more.
Story-wise it's just a short little tale about a human and a youkai, nothing much to say here. However what I would like to talk about is the ending branching. I feel like the choices were a bit too simple? For me, there should have been more choices or ways to split the route branch, such as multiple correct answers that lead you to different paths and affection levels. Yua's reaction to you getting her "What comes after G" question correct could have been an opportunity to explore this for example.
Overall good work! I think there's a lot of potential to be seen.