NO SPOILERS BELOW
Okay, at this point I've gotten most of the way through the ??? route (just missing the true ending).
Overall I was extremely impressed by this game and story. A free game that is fully voiced with this level of detail and plot? Damn. I really like the premise of an otome game but with the same couple in extremely different settings, and I hope that more games try out this style in the future. Obviously having a plethora of love choices is fun, but I really enjoyed seeing the differences and similarities between MC and Kuro through every route, and slowly unlocking more of the overarching plot between the two. Plus its an interesting experiment on differences in character in alternate settings.
And of course as a big fan of yanderes, it was really great to have a whole game around that premise. Detective Route Kuro was my favorite.
I will note that you may want to make it more obvious above that to unlock the secret ending, you need to be on the same save file. I learned that after already having unlocked almost all the endings in different saves, which was unfortunate. For players, take lots of notes for the ??? route, tbh I'm usually a lazy walkthrough follower so had to actually make some effort here (and am still trying on the true ending), haha. The rest of the routes were pretty intuitive though, I liked getting to go back and rechoose instead of having to save every time. That was a nice mechanic.
I would have preferred Kuro's sprites to look more mature in the routes, but it didn't take away from the game enjoyment, just a preference. His and the MC's sprite variations are adorable though.
Overall great job, MM!