Hi! You're correct.
The routes are divided into the three different routes once you finish chapter 5, where you get this image to choose which one you want to continue on. From there the demon chapters would be 6.1 (following in 7.1, 8.1... etc) the human chapters would be 6.2 (and 7.2, 8.2...) and the angel chapters would be 6.3 (following in 7.3, 8.3....). And yes, each update corresponds to a different route, alternating the three in the same order.
So to play all chapters you have to have different savegames (at least 3) from the end of chapter 5.
I hope I have helped to make things clearer for you! And thank you for your support! <3