there's no menu in this, from what I can tell, like there is in most VNs, with the option to save/load the game, so how do I save?

Once you're in the game loop proper, there's a save / load menu. You'll need to go through the introductions for each of the girls and be recruited into the photo club first. The save / load menu will first appear in your dorm room after you've been through these introductions. It's then available at most times a menu is displayed.