I adore this in almost every single way! I happened to play the perhaps "best" route order on my first try (Unum -> Septem -> Nulla), and the way the lore unfolds across the three routes is just perfect (*chef's kiss*). Everything about the game speaks to the amount of effort you have put into it. The PLOT, the sprites, the music, the CGs ... Oh god, the CGs!
I was feeling a bit bad after making a certain choice in Unum's route because that guy is just a brat child who doesn't know better, and then a certain CG came up, which made me laugh every single time I remember it. Speaking of which, just a tiny suggestion: Would it be possible to add a CG gallery to the game, too? Your art is truly gorgeous, and I'd love to revisit them from time to time. :) But no pressure, of course.
All in all, I can't believe this is just Act 1, and I just can't wait to see what you may develop in the future!