Hello, thanks for stopping over here and enjoying the game!
For answer your question, during Act I (Month 1 - September) the 3 routes are being developed continuously, so in each update there will be a progress of the story of the 3 routes available at the same time, as it's in the Demo.
And during a certain point in the story, between Act II or III (Month 2, 3 - October, November) probably I take the decision of develop the story of 1 route at a time for the game (due to to the endings I have in mind).
I know the answer sounds a little vague, but I try to avoid saying any spoilers that I have in mind for the game, hehe.
Once again, thank you very much for playing and also enjoying Kaito's character.
I have many plans for him during the development of the game.