I feel like I'm guessing most of the time, and the lack of a journal to keep track of important details or how events will turn out after I've encountered them at least once would be a very helpful QoL feature. An options menu to adjust sound settings at least would also be nice.
But above all else, I feel the game lacks a motivation for its main objective. Outer Wilds, which I'm guessing is the main inspiration here, has the sun exploding on you at the end of a loop. Similarly, Majora's Mask has the impending moon crash. The Forgotten City also threatens the player with death/petrification if they make grievous mistake.
What I'm getting to is that, time loop games generally give the player a very clear reason to figure out their mysteries, be it the reason for time looping itself, or just persisting the loop ourselves until we stop or circumvent the "imminent doom" part at least. It's an easy way to immerse the player into the role.
This narrative doesn't clearly do that, so I don't feel particularly motivated to resolve the problem. So instead, I find myself trying to solve the smaller problems, but I can barely make any progress on any of them because I'm supposed to do them in a specific order, at least from what I can see.
In summary, I feel it was a major flaw in the process of making the game that a major visible threat to the player (Mizuchi)'s existence wasn't included from the beginning. Even if it is a bit cliched or forced. I was thinking something like, Reimu suddenly deciding to "Fortune Teller" Mizuchi at midnight could work, or someone else if you happen to be possessing her at the time (or not? It could be a major twist if the perpertrator wasn't who we thought it was)
This isn't to say I don't see myself replaying this. Despite all my searching, I couldn't find where KogaBanki was, and I couldn't resolve whatever issue there was with Mokou and Keine, even though I had a hunch what it was. Those are my main motivations to replay the game next time it gets a (major) update.
To end this review on a positive note, I do think the writing is top-notch and the art is very well-made.