I have to say I really like this game, although I have similar thoughts to what was said above. This game has tons of potential. The altered world ending, to my liking, should include a postgame where you can explore the city just as it is seen in the ending. Now that there would be many more NPCs at all hours of the day, Riho should be able to join and have a mini-event. It would also be nice to be able to meet other characters in the cast in random events around the city that change depending on the level of world alteration.
I think the problem with this game is that its foundation and presentation are so good that it offers much more than what was created. There's a lot to squeeze out. I'd say it's a very long-term project that should receive updates with more content for quite some time, with small events at each level of world alteration and with all the characters, since they all have their own charisma (the villain deserved many more scenes of her own around the school; being classmates and never seeing each other is a huge waste).
This doesn't mean that the game is excellent, so good that it makes you want more.