The game is not over, its possible that Dev will loop around later and allow you to have a relationship with both.I think having to choose routes from the menu just to see the new scenes and then go back to how you had it before because otherwise you won't be able to see things from the next update... It takes you out of the immersion of the game a bit. If it keeps branching like this in the future you'll have to play with multiple saves at once choosing different options so you don't lose content... I'm not a fan of these types of games, and having your saves deleted with each update doesn't help.
I mean it would be a real treat to have Yasuka and Noriko together.
That being said sometimes you have to respect Dev for having their vision.