That's also a problem. I played for three hours and lost all my progress because my roomie woke up and I had to get off the computer. They aren't going to wait for me to reach a save point in an eroge. We both play erotic games, but this is the first that doesn't let you save except at specific screens.
I don't know why you disallow saving except at the end of the day… I can't imagine there's any benefit to anyone.
Animal Crossing use to require you to use a your bed to save; but the newest game lets you save anywhere. So, I can see some logic to saving when you go to bed for emmersion; but the logic doesn't really sit well with me for a NSFW game — a game for adults, who usually have less freedom when it comes to their gaming times — which may need to be closed quickly for any number of reasons.
If the autosave actually saved (my roomie's laptop often wipes files that aren't created manually), then I can at least start from the beginning of the first actual day with some of my character progress from the prologue(?) still intact.